Initial drop of NDK plugin sources - with substantial cleanup/renaming/m...

...odificated usage of configuration options

Here is the initial drop of the plugin source (based on Android Maven Plugin master/trunk).

Out of the box, this provides support for static/shared libraries & injection of those into the reactor for use by the Android Maven Plugin (no changes needed).  

**CONFIGURATION HAS CHANGED**: Although most of the configurable options are still available, many have been renamed mostly for clarity and consistency.  Please expect some more changes to come!

Minor enhancements for now:
- Support for multiple attached artifacts from a single build (using additionallyBuiltModules configuration)
- Auto-detect toolchain from available set (highest->lowest)
- Initial support for ARM/X86 64-bit toolchains

Current limitations/dramatic changes in features:
- Support for AAR/APKLIB depdencies for **native** library compilation dropped
- No mixed projects (native/java) is currently supported - use separate modules & dependencies for now