Fix Android build using Urho3D as external library.

Also:

- Enhance generated Eclipse project setting file to additionally use gcc/g++ error parser.

- Enhance cmake_gcc.sh script to fallback to find alternative CMake toolchains directory.

- Enhance Rakefile:
    - New scaffolding task to create new project using Urho3D as external library. At the moment only works in Unix-like platforms.
    - Build in Debug mode instead of Release mode as it should capture more potential issues.