Validate view_state against type of view currently on map

[kylebarron]

# TODO: change this view state to allow non-map view states if we have non-map views   
view_state = ViewStateTrait()

https://github.com/developmentseed/lonboard/pull/908/files#diff-e7dceee3bec447cc53fc7daaa27fe21a525c5a565e82c206461c83c5d83e62bdR155