Fixes #66 : corrected font scaling mechanism
Removed temporary prevFontSize references and used persistent values
from PreferencesManager instead.
fixed #67 : Font slider now appears properly after exiting Preferences
Added font slider display section to DuckDuckGo.onActivityResult
Merge pull request #68 from duckduckgo/font-scaler-fix

Font scaler fix
Merge commit 'b63050a7e104ee3bc00e20feaa1afbca774f29c3' into actionbar-fragments
Lots of changes about font scaling mechanism
not keeping font sizes as DDGControlVar.mainFontSize, instead applying
font size difference globally via DDGControlVar.diff and
DDGControlVar.diffPixel

Conflicts:
	src/com/duckduckgo/mobile/android/activity/DuckDuckGo.java