* Android build scripts: Changed default SDK level to 21; enabled specifying NDK_PLATFORM environment variable for custom SDK level; misc cleanup of Android build scripts
* Update android-aar.sh
I forgot to hit save on the script after making this change locally. The script works either way but by setting this value again in android-build.sh people can more easily build arch specific binaries if they want so the export is unnecessary but also rather meaningless.
* Added script to generate all android versions and script to create AAR with prefab
* disable-pie so x86 static lib works. Update AAR to fix bug related to soname field in .so files themselves. Integrate android-all.sh into android-aar.sh
* Missed updated android-build.sh in last commit. This adds --disable-pie to the configure flags
* Added message after android-aar compilation explaining aar usage