Eliminate the concept of 'Recipients' (plural). There is now just
a 'Recipient', which contains an Address that is either an individual
or a group ID.
MMS groups now exist as part of the group database, just like push
groups.
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This was a holdover from Signal's origins as a pure SMS app.
It causes problems, depends on undefined device specific behavior,
and should no longer be necessary now that we have all the
information we need to E164 all numbers.
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1. Switch from 300 to 500 colors.
2. Colorize incoming conversation bubbles.
3. Colorize recipeint preference activity toolbar.
4. Support inverted colors in avatars.
5. Make status bar icons tint according to secondary color.
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If the contact doesn't have an image, render a color-coded
background and the first letter of the contact's name.
1) Don't display anything during recipient resolution.
2) Display a # icon in material gray for recipients with no name.
3) Display a material group icon in material gray for groups with
no avatar icon set.
Closes#3104
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