safeslinger release 1.6.13

- Added Forgot Passphrase? feature to generate new key.
- Added Add Contact Invitation feature to select a contact to send
Sling Keys instructions to.
- Added easy access logout from the passphrase cached notification.
- Added automatic logout when airplane mode is turned on.
- Two-user key exchanges will now pre-select the imported key to draft
a new message.
- Improved accuracy of passphrase timeout when idle.
- Corrected several issues causing sent messages to delay or duplicate
themselves.
- Stability fixes.