* Fix sizing of the unread indicator cells.
* Fix conflicts between paging and “load window” of conversation view and unseen indicator.
* Modify unseen indicator to indicate whether there are more unseen messages and safety number changes.
* Fix conflicts between modifying the “load window” size and updating the dynamic interactions.
* Clear the “bubble size calculator” cache whenever the view changes size.
* Improve the scrolling behavior around “load more messages”.
* Improve management of “load window” size.
* Fix issues around caching of bubble sizes.
// FREEBIE
* explicit optional usage in strings
* remove some unused StringUtil code
* swiftlint affected files
* more concise optional casting (and avoid a `!`)
Compiler warnings: 343 -> 318
(Actually most of these are in external libs, but 115 remain in Signal/SSK)
// FREEBIE
* Add support for contacts with more than one Signal account using ContactAccount class.
* Use OWSTableViewController in contact-related views.
* Let users add non-contacts to groups.
* Improve the "new group" and "edit group" views.
* Add utility methods for displaying alerts.
* Warn users before discarding unsaved changes in "edit group" view.
* Pull out "contact view helper" to de-duplicate common logic among contact-related views.
* Pull out "group view helper" to de-duplicate common logic among group-related views.
* Pull out new base class for view used to add accounts to groups or the block list.
// FREEBIE
This assert was being falsely triggered by legitimate unicode.
The current state of affairs (unchanged by this PR) is that all
diacriticals will be stripped from a message that also contains e.g. 3
flags in a sequence.
// FREEBIE