Wire up map settings UI

Summary:
- Hide unneeded/unimplemented options
- Clean up template
- Show a real map view in map preview
- Wire up map preview to reload when settings changed
- Geocode 'default location' and set map center

Fixes T97

Test Plan:
- Enable map settings feature
- Go to map settings
- Try out various config options, save and check settings appied

Reviewers: dkobia, eyedol, shadowhand

Reviewed By: shadowhand

Subscribers: srutto

Maniphest Tasks: T97

Differential Revision: https://phabricator.ushahidi.com/D197