Initial geolocation_context schema

- Fixes #22
- cc @alexanderdean for snowplow/snowplow#950
Fixed typo in longitude

Thanks @alexanderdean
Added new properties & required fixes
Renaming accuracy to latitudeLongitudeAccuracy
Renamed heading to bearing

- It's more accurate than 'heading'
Switched declaration order /cc @jonalmeida
Merge branch 'feature/geolocation_context'
Added geolocation_context into Release 4