Avoids the known hang, which was caused by getting stuck in a loop setting the frame back and forth over and over. Looked like it was adding and then removing (and then adding, etc) the height of a single line of text. Possible the username was shifting back and forth between truncating and wrapping, but have not confirmed that.
Fixes#705 IOS client consistently hangs when writing new post at ~= 150 chars
A large amount of change primarily to the view model layer, to make reasoning about the content reveal/hide state easier.
To prevent terrible scrolling jags while allowing the cells to be shorter when hiding content, the layout changes for content display state now happen before the cell is returned by the datasource provider and the tableview is reloaded when a status’s display mode changes.
- split ComposeContentViewModel.Kind into Destination (top level/reply) and an initial content string
- replies get the mentions prepended to the initial content string
