Add initial doxyfile
Clarify project description
Tweak doxyfile
Add generated documentation to .gitignore
Start documenting Texture class
Document Wav class
Move Doxyfile to project root
Define documentation groups
Merge branch 'master' into doxygen

Conflicts:
	README.md
	SDL2pp/SDL2pp.hh
Document Window class
Document Exception class
Document SDL class
Fix groups
Add Texture to the group
Merge branch 'master' into doxygen

Conflicts:
	SDL2pp/SDL2pp.hh
Document AudioSpec class
Document Texture::LockHandle and AudioDevice::LockHandle classes
Document AudioDevice class
Move whole descriptions into documentation headers
Reference SDL as SDL2

Also makes % which disables autolinking uneeded