Build script to build web apps
    1: Add android build script android/android_build_app.py
    2: Add common build script make_webapp.py for both android and tizen

    How to use:
    Build all apps for both Tizen and Android
        python make_webapp.py
    Build specified app
        python make_webapp.py --app=MemoryGame
    Only build for Android
        python make_webapp.py --target=android
    Update Web Apps and then build all of them
        python make_webapp.py -u

    The build result will be under out directory

Scenario:
1: Find all the available web apps : (Which contains manifest.json)
2: Init update all web apps
3: Check whether build script exists, if no, hook downloader to download the specified version
4: Loop all the apps
5: Copy manifest.json to [WebApp]/src
6: Build with build script
7: Remove manifest.json
8: Move the build result to out folder