propose splitting map subfolder into map & data

[incanus]

It's getting unwieldy with things since #928 and with work on #893.

I propose moving the following into <mbgl/data/...>:

• *_tile.* (4)
• *_tile_data.* (8)
• *_tile_parser.* (4)
• tile.* (2)

This would leave in <mbgl/map/...>:

• environment.* (2)
• map.* (2)
• source.* (2)
• sprite.* (2)
• transform*.* (4)
• view.* (2)

I can handle this as part of #893 since I'm starting to add some Annotation* classes as well.

/cc @kkaefer @jfirebaugh

[jfirebaugh]

Sound fine, but we don't need to do this right now.

[kkaefer]

Agree with @jfirebaugh