Implement ctrl + scroll wheel for increasing and decreasing font size

[GoogleCodeExporter]

For improved accessibility. 

I'm not sure if this should be a temporary zoom feature, or actually change the 
font size and be persisted in the settings file.

Original issue reported on code.google.com by stephen....@gmail.com on 13 Apr 2012 at 7:24

• Blocked on: Add UI settings for Font Family and Size #23

[stephen-swensen]

fixed by pr #51