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)
Yes it has to be the first line (as a good practice). But we can do that, it could potentially affect behaviors of commands though, but I wrote everything based on 2.8 so it is ok (for now), fortunately this would be the only platform where we'd have to do that.