Post peer review changes for @dhensby and @willmorgan (+4 squashed commits)
Squashed commits:
[cb48beb] Allow optionally setting an api key. Use new google apis endpoint.
[dd913ff] FIX: allow front-end usage, by running entwine code only if entwine is loaded
[ed15e81] Make search box optional
[3fd0d88] Install to 'googlemapfield' folder via composer, instead of 'silverstripe-googlemapfield'
Mega documentation update
composer.json: bump to 1.3, fix keywords
Change apikey parameter to apiKey
Simplify + overhaul config to use Config service

Zoom field work
Clean up dependency management in Field
minor JS: remove email