Introduction of the new "About application" page (pull request pending)

Introduction of a new "About application" page

This commit adds a new "About application" page with

+ version number from Manifest
+ urls: url text and link for license, ~~list of changes~~, support, bugreports
+ copyright text: (C) 2012-2014 Open Whisper Systems
+ easily extendable
+ based on concepts as found in https://github.com/schildbach/bitcoin-wallet
+ theme-aware "about" page