Added Java JNI install support

Added support for Java JNI installation:

  * Java JNI classes are inside org.radare.radare2 package.
  * All java stuff is installed under ${PREFIX}//share/radare2/java/jni/[jar|lib]
  * Fixed the test example to compile.

To compile the test example just:

 `javac -Djava.library.path=$PREFIX/share/radare2/java/jni/lib/ -cp .:$PREFIX/share/radare2/java/jni/jar/radare2.jar TestRBin.java`

To execute the test example:

`java -Djava.library.path=$PREFIX/share/radare2/java/jni/lib/ -cp .:$PREFIX/share/radare2/java/jni/jar/radare2.jar TestRBin`