Adding core base files for raspberry Pi

- libtess2 is linked as a share library
- in the documentation I put how to switch the cmake version to avoid compiling cmake-3 on the rpi
- Pan gesture only (using mouse devices)
I see, you're right that it's probably not good practice. The better solution is probably to figure out what's going on in the iOS cmake files that breaks without 3.0 (The iOS toolchain claims to only need 2.8)