Allow entering Space URLs without a trailing slash

Note that this is done in the context of Nested Documents.

The idea is to allow users to enter /A/B and that it would lead them to A.B.WebHome.

Implementation details:

• We would do this only for the "view" action since we need to keep backward compat as much as possible for existing apps which use the inline or edit action to create new pages. Otherwise they would end up always creating non terminal pages when they may want to create terminal pages and they may fail as a result (for example if they search for all docs in the current space). It's better to let these apps be upgraded one by one to decide what they want to do.
• When /A/B is requested, if A.B exists then go to it. If not, verify if A.B.WebHome exist and if so forward to it.