Replace mapbox-gl-vue library

[solebared]

We currently use the mapbox-gl-vue library to bring mapbox-gl into our vue codebase. Unfortunately, that library uses an incompatible license (GPL 3.0) and also appears to be unmaintained.

Needs to be replaced either with a similar library or alternatively, our code refactored to use Mapbox GL JS w/o an intermediary.

See #755 for further discussion.