change out key cached icon to be more unique

Fixes #651
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Merge pull request #1495 from mcginty/icon-cached

change out key cached icon to be more unique
don't call replace() on null formattedNumber

Fixes #1397
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sanely handle duplicate contacts in db

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Play Store text changes: github URL corrected, support URL added
Always allow resend in Conversation details menu
added "not connected to a google account" to registration problems list
rewording screen security setting text

+ fix for issue #1360
add CHANGELOG.md #1161
add CHANGELOG.md and translatable version /res/values/changelog.xml
Introduction of a new "About application" page

+ version number from Manifest
+ urls for license, list of changes, support
+ based on concepts as found in https://github.com/schildbach/bitcoin-wallet
+ theme-aware page (dark/light design)
+ returns correctly from web pages (like source code, support forum) to the About page
+ (C) 2014 Open Whisper Systems
+ obeying code style guidelines
use localized timestamp format for message details

+ fix for #1419 (Delete leading zero from fragment timestamp)
Add possibility to delete contacts' identity and directory entries.

+ fix for #274
+ could be a way to remedy #791:
  deleting the wrong number from the directory,
  adding the next one on the next sync
translatable msg details: status format strings

* strings for the message details allow i10n/i18n
** transport method strings ("PUSH", "MMS", "SMS")
** transport status ("pending")
* #562 partial fix: additional new lines in message details
add notification for key change event, fixes #1460