cryptic error when running a model not supported by the language

When running a model for a language that is not supported (either directly or via melange adaptation) the error is not self explanatory : this is currently a stack trace such as:
```
java.lang.RuntimeException: java.lang.IllegalArgumentException: argument type mismatch
at org.eclipse.gemoc.execution.sequential.javaengine.PlainK3ExecutionEngine.executeEntryPoint(PlainK3ExecutionEngine.java:283)
at org.eclipse.gemoc.executionframework.engine.core.AbstractSequentialExecutionEngine.performStart(AbstractSequentialExecutionEngine.java:86)
at org.eclipse.gemoc.executionframework.engine.core.AbstractExecutionEngine.startSynchronous(AbstractExecutionEngine.java:333)
at org.eclipse.gemoc.executionframework.engine.core.AbstractExecutionEngine$1.run(AbstractExecutionEngine.java:316)
at java.lang.Thread.run(Thread.java:748)
Caused by: java.lang.IllegalArgumentException: argument type mismatch
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.eclipse.gemoc.execution.sequential.javaengine.PlainK3ExecutionEngine.executeEntryPoint(PlainK3ExecutionEngine.java:271)
```

We should, a minima, propose a better message that indicates which object was passed as argument versus the expected one (full java name should help)

In addition, the launcher can be improved in order to clearly indicate the issue before launching the model.

Note : this error is quite recurrent especially since the process of building a simple language is not correctly documented compared to the process of build 2 languages via extension (see user who had related issues : https://github.com/gemoc/gemoc-studio/issues/59 https://github.com/gemoc/gemoc-studio/issues/61 )