Page - Change title when adding a new element

This issue has been migrated from mozilla/webmaker-android#1977.

It was originally written by flukeout on Thu May 21 2015 and had the following description:

Spec shows the dark overlay covering the entire page, but currently the header is not covered.

Spec

On Thu May 21 2015, thisandagain commented:

This will likely be really difficult as transparent Crosswalk webviews aren't a thing. Alternate would be to rebuild this entire nav using native code. :worried:

On Thu May 21 2015, flukeout commented:

How about changing the header to say "Add an Element" while in this state?

On Thu May 21 2015, thisandagain commented:

That's totally do-able. :+1: