mGerrit: Allow users to add gerrit teams locally

Also adds a handshake warning if the team is behind a SSL connection

Patch Set 3:
 + pass correct Exception to user dialogs
 + Ensure propper url endings for custom team entries

Patch Set 4:
 + Extract Error dialog to new .helpers.Tools
 + Actually show the correct exception
 + Now handle GerritTask exceptions within GerritTask
 - removed GerritFailedCallback (now redundant)
 + Added StackTrace information to error dialog

Patch Set 5:
 + update Volley to c3dea925af9b3523e2e01e8b7799e71ef558c1c5

Patch Set 6:
 + enforce URL requirement of ending in '/'
 + code clean up
 + Long click user added gerrit teams to remove from list
 + prefill url with text "http://"
 + stricter requirements for valid URL text

Change-Id: Ifac2a7c3f3157226b30e28976a757df729263437
Merge "mGerrit: Allow users to add gerrit teams locally"