Change "Modules" nav link to "Settings"

- Changed “Modules” in navigation to “Settings”, which makes more sense
to me.
- Improved resolution of module icons, by changing font-size to 16px
Change "Modules" nav links to "Settings"

- Changed “Modules” in navigation to “Settings”
- Improved resolution of module icons, by changing font-size to 16px
Merge pull request #472 from Automattic/ui-tweaks-dave

Ui tweaks dave