Big (intitial) update to how textures are handled.

Textures will now be wrapped in MapTexture, but should only be
instatiated by sub classes of MapTexture
Text texture wrapper added
#6 Slow work towards a good way to swap tiles. key 1,2 and 3 swap
between some images (3 is a real tile)
fixes #5 Only a single tile can be added to a single square. The tile
must be removed before another can take its place (this might be
adjusted later)

Zoom has also been added
Minor change (formatting)
Left menu tile display added, funtionality to come #4