Behaves similarly to the DatabaseUpgradeActivity. You have a
static list of ExperienceUpgrade models that include a "trigger"
version, where when a user upgrades through it a notification
will appear, and there will be a splash explanation screen.
Right now the splash screens are basic and not too configurable,
but that can be reworked as upgrades demand.
Closes#4151
1) orientation changes are now properly handled
2) emoji panel will not overrun the actionbar and composition area
in space-contentious situations (quick reply popup)
Closes#3553fixes#3501fixes#3485fixes#3199
// FREEBIE
