add build scripts to directly build with ant

I personally hate Eclipse, so I decided to figure out how to build with ant (the Java build system that eclipse uses internally). 

Ant requires two environment variables - ```ANDROID_HOME``` and ```NDK```.

ANDROID_HOME is the path to the android SDK folder. for example:
``` ~/me/programming/android/sdk``` would be your ```ANDROID_HOME``` path.

NDK is the path to the [Android NDK](http://developer.android.com/tools/sdk/ndk/index.html) on your machine. It's used to compile the C++ side to things (which interfaces with the Java code). For example:
```~/me/programming/android/ndk``` would be your NDK path.

Once these two paths have been exported (export them by adding these lines in your ~/.bashrc (or) ~/.zshrc), go to ``` ppsspp/android ``` and run ```ab-ant.sh```. This script does 3 things:

1)  build the project and generate ppsspp-debug.apk
2)  install the ppsspp.apk into your phone
3) run the main activity in the ppsspp apk.

It's nicer since you can automate it to build every time you save / every time you push (or) whatever is up your alley :)  Just decided to add this for anyone who wants this info

Note - this does *not* break ab.sh. You can still compile just fine by first running ab.sh and then use Eclipse.
This is just a faster one-step process.