update gradle build version. add .idea dir to gitignore

updated main build.gradle and ActionBarSherlock build.gradle files to use gradle
version 1.12.1 and buildToolsVersion 19.1.0 to support current version (0.8.3) of
Android Studio. Also added .idea directory to gitignore as these are local files
generated by Android Studio (IntelliJ).
fixed several build errors. updated to gradle 0.12.1

updated paths in android.mk to relative paths so that ndk-build wont fail.
modified build.gradle so that generated *.so files will be copied to the correct
intermediate directories for adb packaging. fixed some additional errors in
jni_glue.cpp which were causing build errors. Debug builds were tested with Android
Studio 0.8.3 and release builds tested from a modified version of the existing command
line build script. both on OSX 10.9.4

added