GUI enhancement: make choice of default context in starred view clear

[C-Otto]

I fail to understand how the default context is set in the starred view. I expect the topmost context (as defined in the context view) to be used, as it is done on the front page. However, it seems to be related to which contexts actually contain starred actions - and the choice of which context to use in the form is made without regarding the contexts' order.

[C-Otto]

The current code takes the context of the first starred action, ordered by creation time. This specific choice is not meaningful in any way.

[C-Otto]

Introduced based on this discussion: https://www.assembla.com/spaces/tracks-tickets/tickets/868#/activity/ticket:

I took the initial request one step further and provided a better initial context (if there are multiple contexts covered by the tag it does nothing clever, it just takes the first).

Also in that discussion:

It seems to me that the "better" initial context may only be better for some people. That should go in a different ticket, at least.