more responsive enter key on map search. added 'locate me' button.

Lots of UX improvements including
- pressing the Enter key fires off a request that automatically takes the first result once responses are loaded
- new ajax responses abort old ajax responses
- 'locate me' button complete with custom icon
- a fix for 1022620 "Change map zoom setting based on available information (/user/edit page)" 
- removed redundant jumptoGeocode() function
- moved init code block inside reverseGeocode() to INIT section
- improved INIT logic when no coordinates found (runs a search with all available text)
- tons of cleanups & a few more code comments

relevant bugs:
https://bugzilla.mozilla.org/show_bug.cgi?id=1015334
https://bugzilla.mozilla.org/show_bug.cgi?id=1022620
This is missing `display_country.text(mapbox_country);`