Include NDK_PROJECT_PATH in env

This seems necessary for ndkBuild with jni sources under src/main.
Merge pull request #82 from mrdomino/master

Include NDK_PROJECT_PATH in env
0.13 changes
0.13 changes for 0.9.2
0.13 changes for test hello-world-oscarvarto
0.13.5 changes
fix #65 add AutoPlugin support, auto-enable with AutoBuild
Add aliases for AutoPlugin autoImport

aliases added for ProguardCache, ProguardInputs, apklib, aar,
AutoLibraryProject and LibraryProject
Try to disable automatic plugin enablement...
Change autoImport to be Keys directly
create a new test case for #60, unable to repro
Add language.implicitConversions to Keys