Moved calculation to their own functions
Moved drawing code to separate thread

Now, the application starts up immediatelly, instead of
waiting for the image generation to finish.
Switched array to use atomic operations
Moved drawing completion code to idler function.

This makes drawing area invalidation thread safe. The idler
is run by the main loop.
Added support for drawing snapshot images
Use glib RNG
Run many threads
Added C++11 flag to documentation