implemented minimum window size
changed minimum window size
added header-guards around view
move view code out of window
set default viewport rect for View
initial stretching support
fixed issue with stretching grey screen in window mode
implemented letterboxing
implemented config file option for viewport_type
fixed issue with letterboxing not greying out properly
new  config file in assets
Merge pull request #12 from vheuken/master

Merging back