None map type & OSM performance improvements

[kfarr]

and new feature -- none!

to test:

• use the new osm3d option, see if buildings look ok for a new location (optional draw call testing [1] but it's tedious and I already did it)
• test new "none" map type -- can switch to / from without problem? does the map attribution disappear for none? can you save and reload and then change to another map type and the location is still retained?

[1] Optional testing draw call improvement on buildings:

Previous (before this PR):

• on a scene with location set and osm3d map type
• run on console: AFRAME.scenes[0].setAttribute('stats','')
• hide the geospatial > osm 2d tiles layer (also hide other street layers that might interfere with this test)
• zoom out to see all buildings and notice that the draw calls increases as you zoom out and see all buildings, then zoom in and observe draw call decreasing

After:

• draw call should not increase / decrease when zooming in and out and looking at osm buildings (also hide other street layers that might interfere with this test)