PythonDetails is not serializable

Nobody has claimed this yet.

`PythonDetails` implements `Serializable` but it takes a `Project` that is not serializable.

If you try to make it so that the `PipInstallTask` gets cached you get an exception that it can't be

```
Failed to execute org.gradle.cache.internal.AsyncCacheAccessDecoratedCache$2@613b3d80.
org.gradle.api.UncheckedIOException: Could not add entry ':PlexxiCorePythonAPI:installPythonRequirements' to cache taskArtifacts.bin (/Users/jonathanleitschuh/work/git/plexxicontrol/.gradle/3.4-20161216120313+0000/taskArtifacts/taskArtifacts.bin).
at org.gradle.cache.internal.btree.BTreePersistentIndexedCache.put(BTreePersistentIndexedCache.java:158)
at org.gradle.cache.internal.DefaultMultiProcessSafePersistentIndexedCache$2.run(DefaultMultiProcessSafePersistentIndexedCache.java:53)
at org.gradle.cache.internal.DefaultFileLockManager$DefaultFileLock.doWriteAction(DefaultFileLockManager.java:184)
at org.gradle.cache.internal.DefaultFileLockManager$DefaultFileLock.writeFile(DefaultFileLockManager.java:174)
at org.gradle.cache.internal.DefaultCacheAccess$UnitOfWorkFileAccess.writeFile(DefaultCacheAccess.java:457)
at org.gradle.cache.internal.DefaultMultiProcessSafePersistentIndexedCache.put(DefaultMultiProcessSafePersistentIndexedCache.java:51)
at org.gradle.cache.internal.AsyncCacheAccessDecoratedCache$2.run(AsyncCacheAccessDecoratedCache.java:48)
at org.gradle.internal.concurrent.ExecutorPolicy$CatchAndRecordFailures.onExecute(ExecutorPolicy.java:54)
at org.gradle.cache.internal.CacheAccessWorker$2.run(CacheAccessWorker.java:187)
at org.gradle.internal.Factories$1.create(Factories.java:25)
at org.gradle.cache.internal.DefaultCacheAccess.useCache(DefaultCacheAccess.java:179)
at org.gradle.cache.internal.DefaultCacheAccess.useCache(DefaultCacheAccess.java:162)
at org.gradle.cache.internal.CacheAccessWorker.flushOperations(CacheAccessWorker.java:177)
at org.gradle.cache.internal.CacheAccessWorker.run(CacheAccessWorker.java:147)
at org.gradle.internal.concurrent.ExecutorPolicy$CatchAndRecordFailures.onExecute(ExecutorPolicy.java:54)
at org.gradle.internal.concurrent.StoppableExecutorImpl$1.run(StoppableExecutorImpl.java:40)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)
Caused by: org.gradle.api.GradleException: Unable to store task input properties. Property 'pythonDetails' with value 'com.linkedin.gradle.python.extension.PythonDetails@79695a29' cannot be serialized.
at org.gradle.api.internal.changedetection.state.InputPropertiesSerializer.write(InputPropertiesSerializer.java:42)
at org.gradle.api.internal.changedetection.state.CacheBackedTaskHistoryRepository$LazyTaskExecution$TaskExecutionSnapshotSerializer.write(CacheBackedTaskHistoryRepository.java:441)
at org.gradle.api.internal.changedetection.state.CacheBackedTaskHistoryRepository$TaskExecutionListSerializer.write(CacheBackedTaskHistoryRepository.java:224)
at org.gradle.api.internal.changedetection.state.CacheBackedTaskHistoryRepository$TaskExecutionListSerializer.write(CacheBackedTaskHistoryRepository.java:200)
at org.gradle.cache.internal.btree.BTreePersistentIndexedCache$DataBlock.setValue(BTreePersistentIndexedCache.java:659)
at org.gradle.cache.internal.btree.BTreePersistentIndexedCache$DataBlock.(BTreePersistentIndexedCache.java:646)
at org.gradle.cache.internal.btree.BTreePersistentIndexedCache.put(BTreePersistentIndexedCache.java:150)
... 18 more
Caused by: org.gradle.internal.serialize.MapSerializer$EntrySerializationException: Unable to write entry with key: 'pythonDetails' and value: 'com.linkedin.gradle.python.extension.PythonDetails@79695a29'.
at org.gradle.internal.serialize.MapSerializer.write(MapSerializer.java:50)
at org.gradle.api.internal.changedetection.state.InputPropertiesSerializer.write(InputPropertiesSerializer.java:40)
... 24 more
Caused by: java.io.NotSerializableException: org.gradle.api.internal.project.DefaultProject_Decorated
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1184)
at java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1548)
at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1509)
at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1432)
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1178)
at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:348)
at org.gradle.internal.serialize.DefaultSerializer.write(DefaultSerializer.java:53)
at org.gradle.internal.serialize.MapSerializer.write(MapSerializer.java:48)
... 25 more
```

The solution would be to mark the `Project` field in `PipInstallTask` as transient.

Start at the PythonDetails and PipInstallTask entry points, focusing on the Project field described in the issue. Reproduce the PipInstallTask caching scenario and confirm that task input serialization completes without the reported NotSerializableException.

Written by the indexing model from the issue text.