Multi App build script

This pull request includes an improved `build.sh` script with the capability of creating multiple apps. Tested with a clean python-for-android distribution where I removed `build`, `dist` and `.packages`. The anontunnel app compiles with a single call to `build.sh` and runs on the android device.

**Important**: I am currently **not** getting output in logcat or the textview about my anonymous tunnel when I start it. It just says "Starting the anonymous tunnels..." and doesn't print anything else. Is this a known problem or did I break something? Do not merge until we fix this!

Improvements:
* Easily create more apps. Each app should have its own `python-for-android.deps` file where you can specify its recipe dependencies.
* No more double building and prebuilding kivy in python-for-android. Tested a single run of `distribute.sh` which works.
* No more recompiling of the entire python distribution.
* Less hard coded paths, which makes SIG happy.

I have also added a `pyconf` app which helps me get some link/compile flags for the android python distribution, in order to build libtorrent-python bindings correctly.