hide screen security when unsupported
// FREEBIE
refactor and improve contact selection

* unify single and multi contact selection activities
* follow android listview design recommendations more closely
* add contact photos to selection
* change indicator for push to be more obvious
* cache circle-cropped bitmaps
* dedupe numbers when contact has multiple of same phone number

// FREEBIE
Handle simultaneous initiate protocol case.

1) Modify SessionRecord to store a list of "previous" sessions
   in addition to the current active session.  Previous sessions
   can be used for receiving messages, but not for sending
   messages.

2) When a possible "simultaneous initiate" is detected, push the
   current session onto the "previous session" stack instead of
   clearing it and starting over.

3) Additionally, mark the new session created on a received
   possible "simultaneous initiate" as stale for sending.  The
   next outgoing message would trigger a full prekey refresh.

4) Work to do: outgoing messages on the SMS transport should
   probably not use the existing session if it's marked stale
   for sending.  These messages need to fail and notify the user,
   similar to how we'll handle SMS fallback to push users before
   a prekey session is created.
Add refresh path for PreKey queue.
Don't display duplicate push messages.
Curve25519 keys to 1 mod 8 for ephemerals.
Fix decryption corner case when passphrase is disabled.
UX for unencrypted fallback case
Merge pull request #1205 from mcginty/contact-select

refactor and improve contact selection
Merge pull request #1272 from mcginty/flag-secure

hide screen security when unsupported
new send icons, fix logic for disabling/enabling
// FREEBIE
Merge pull request #1233 from mcginty/send-icons

new send icons, fix logic for disabling/enabling the button
simplified layouts
Merge pull request #1260 from mcginty/message-layout-lint

Conversation item tweaks
outgoing group MMS should never be encrypted
// FREEBIE
Merge pull request #1248 from mcginty/wrong-group-secure

outgoing group MMS should not be encrypted and considered push
fix send icon merge botch, encryption icons logic
// FREEBIE