Android annotations and longs

Fixes #621 and problems with annotations priority.

The new organization of mnit_simple, and its annotations, means that you can compile any of the test_*.nit and it will create a `.apk` with a distinct package. Thus they can be installed side by side, but they all have the same display name :(

Using Java `long` on Android works again, but they are not fully compatible with Nit's `Int`. Java's `long` are on 64 bits, and Nit's `Int` on 32 bit under ARM. There may be data loss.