adds topOffset attr to acMap Directive

Needed a means to set the height of the map container explicitely.

see:
https://trello.com/c/s2Xtnmdk/274-issue-excessive-clicking-causes-freezing-and-to-dissapear
and
https://trello.com/c/xEmdC3l2/224-bug-on-mobile-the-more-arrow-loads-in-the-right-place-then-shifts