[Epic] Improvements to Java Runtime avoid com.sun.*, support MANIFEST main and other runtime image optimizations

The following are list of tasks that we need to work to improve the OW Java Action runtime:

1. avoid usage of com.sun.* packages - this is used in https://github.com/apache/incubator-openwhisk-runtime-java/blob/master/core/javaAction/proxy/src/main/java/openwhisk/java/action/Proxy.java, instead we can use readily available pre-built httpservers e.g. using vert.x is one of the options for high performance

2. Right now we rely on the `--main` parameter passed to run Java Aciton, instead we can make the Loader to infer it via `MANIFEST.mf` **Main-class** or add custom attribute for OW apps

3. It would be great to have making OW Java Action use standard Java main method signature with just `String[] args` and we define custom Launcher that convert the args to JSON and delegate to OW Java Function Launcher, this way it will be easy for applications to be built and tested outside before testing in OW
Edited by @csantanapr 3 is now a new issue: https://github.com/apache/incubator-openwhisk-runtime-java/issues/15

@csantanapr @ddragosd @gorkem - thoughts comments and feedback ??