Updates for Location fields Google Maps UI

Hi Jed,

As promised, here is the PR. 
I have implemented the <code>{map:true}</code> and 'Select point on Map' UI button as you suggested. 

I also am using [http://hpneo.github.io/gmaps/](gmaps.js) dependency if you guys don't mind. 

I am trying my best to place the code where it belong (pls guide me on this). If there is a mistake on that part let me know, i will do another pr to fix it.

Your Comments are most welcome! :)