Change package and namespace to Java rather than IdrisJava.

[jfdm]

Question: Would it not be better to call the package java? As we are already in Idris, the Idris in the IdrisJava namespace seems a little redundant.

If I have time I shall make the alterations myself and issue a PR, but thought it worth a mention in case anybody agrees and wishes to contribute a PR. Also I have no idea how this would affect upstream dev..

[bgaster]

I would prefer not to change the package name to Java, for two reasons:

1. I followed the naming convention of IdrisScript, the Javascript backend:
   https://github.com/idris-hackers/IdrisScript
2. In a application I've written for automatically generating FFI interface for Java method prototypes, there is a library for Java syntax and parsing, packaged under the name Java.

[jfdm]

Ah okay. Thought it was worth a mention. Personally, I liked the approach taken in the python backend (ziman/idris-py) where the namespace is Python a little bit cleaner.

[Melvar]

There should definitely be a convention for the names of backend-FFI libraries. The question is how to come up with one.