Add some documentation bits
Drop hardcoded values only working for zoom 16 in Koblenz
Reduce rendered tiles size

Improves reaction time when changing the zoom or starting the application
Limit zoom to valid values (1 to 18)
Ignore more cmake files
Use a define to set the path
Ignore the Makefile also
Start adding more checks to the build system
Improve build time by moving the boost asio from the header to the cpp

Parsing the header is really expensive, it might be worth looking at precompiled headers though,
because this looks hackish because we loose the class encapsulation.
Use proper library lookup for all libraries
Drop unused command line parameters