Moved SWIG code from C++ files (hpp and cxx) to SWIG interface files (.i). Added getter/setter methods for classes with protected or private vars.

src/grove/javaupm_grove.i

@@ -49,4 +49,12 @@
     #include "grovetemp.hpp"
 %}
 
+%extend upm::GroveButton {
+    void installISR(mraa::Edge level, jobject runnable)
+    {
+      $self->installISR(level, mraa_java_isr_callback, runnable);
+    }
+}
+
+
 JAVA_JNI_LOADLIBRARY(javaupm_grove)