Move all user interaction - share room already present and share room not
found - out of the share rooms collection and into the share rooms view.

The already-intricate provision for toggling share room remembering for
already present ones would get even more intricate, so just drop it.
Merge branch 'issue-102-move-ui-stuff-to-view' into issue-102-transient-feedback
Use new spiderOakApp.dialogView.showNotify() to show a transient dialog
from AddShareRoomView.form_submitHandler().