Changed mouse input to CanvasRenderer, Tools now activate from outside
of canvas, e.g. you can start a brush stroke or selection from outside
canvas and drag it in. This is the same behavior as Paint.NET*

*Right now selections are not clipped to canvas bounds however
Centered Canvas, also fixed lastbutton from last commit
Lightened transparencyBGDark when in Dark Background mode, was often
hard to see what I was doing
Added Normal/Dark background to UserPreferences
Added image size label, not the most elegant, but workable
Added mouse coords label:
 * coords at any time
 * coords dragging to
 * area of selection
Merge pull request #57 from BurntPizza/dev

more tweaks/fixes