Update summary in TimePreference change listener

Ensures the summary is updated even if we change the time preference
programatically; also allows other places to stop the summary from being
updated by setting a new listener.
Allow sending of any filetype via intent

Fixes #756
Handle time comparisons using longs
properly count mam messages
Merge branch 'issue756' of https://github.com/SamWhited/Conversations into SamWhited-issue756
properly detect images in share with
Merge pull request #783 from SamWhited/quiet-hours

Update summary in TimePreference change listener
smoothed out scrolling a bit
made scroling smoother + bug fixes for history loading
Merge branch 'development' of https://github.com/siacs/Conversations into development