Let users set #REDIRECT and __STATICREDIRECT__ status

Adds setting and unsetting the #REDIRECT status of the page from the page
settings pane of the meta dialog, and toggle whether this is a static
redirect (i.e., it is not automatically changed when its target is moved).

If the page has a redirect set, the meta dialog will be shown on opening
the page so that users can adjust the redirect more swiftly.

Bug: 47328
Bug: 50878
Bug: 57173
Change-Id: Ibd89cf04486799f292b9fd045dae5bc23fcf6fd4
Merge "Let users set #REDIRECT and __STATICREDIRECT__ status"