SWIGJAVA: Remove the last JAVA ifdefs from src

Removed all references to #ifdef SWIGJAVA and JAVACALLBACK from the
library source.  All java-specific source code has been moved to the
corresponding library's .i file for java.

    * Update library source
    * Update examples where necessary
    * The function pointer methodology has been remove from libraries
      which provided callbacks as both a class and a function pointer
      implementation.  Examples were updated to use the class version
      of callbacks.
    * Updated documentation for SWIGJAVA

Signed-off-by: Noel Eck <noel.eck@intel.com>

src/button/button.hpp

@@ -87,11 +87,8 @@ class Button{
          * @param arg Pointer to an object to be supplied as an
          * argument to the ISR.
          */
-/*#if defined(SWIGJAVA) || defined(JAVACALLBACK)
-        void installISR(mraa::Edge level, jobject runnable);
-#else*/
         void installISR(mraa::Edge level, void (*isr)(void *), void *arg);
-//#endif
+
         /**
          * Uninstalls the previously installed ISR
          *