General Optimizations to new application design

[jjnesbitt]

Makes the following notable changes:

• Update the models to include new fields / indexes
• Update the behavior of vector map layer / tile retrieval, to make use of tile_extents, a field which contains the range of x/y values for every z depth in the VectorMapLayer
• Remove local paths for docker-compose service volumes (will need to re-run database migrations and population)
• Retrieve all map layers from one dataset endpoint, instead of two-staged approach