* Ubuntu missing fonts (fixed path)

* detailed instruction on building on linux

* fixed truetype fonts paths for linux + bring back TTF paths

* More const correctness
* Converted "map.insert(make_pair(a,b))" pattern into "map[a] = b".
* removed some warnings (e.g. double->float conversions and sign mismatch)

- Change file structure to separate code from data and 3rdparty binaries.
- Move from make and VS solutions to cmake build system.

neither midi nor the keymap stuff are intrinsic to SDL