Added Auto-Display My Collections Capability

When someone logs in, if they logged in via the My Collections menu item
then start their session by displaying My Collections. If they logged in
via the log in icon then start their session by displaying their default
collection, which is the current behavior. Note that the user should not
go automatically to My Collections for the remainder of their log in,
even when visiting their default collection later. The only other way to
get their during their log in is by clicking on My Collections.

See https://trello.com/c/tSzd00zu/199-start-with-my-collections-option
for details.