[WIP] Bitmap and Bitmap Tile Layers

[jtmiclat]

Addresses #206
Example usage:

import geopandas as gpd
from lonboard import Map
from lonboard._layer import  BitmapLayer, BitmapTileLayer


layer = BitmapLayer(bounds=[-122.5190, 37.7045, -122.355, 37.829],image='https://raw.githubusercontent.com/visgl/deck.gl-data/master/website/sf-districts.png')
map_ = Map(layers=[layer])
map_

and

layer = BitmapTileLayer(data='https://c.tile.openstreetmap.org/{z}/{x}/{y}.png')
map_ = Map(layers=[layer], _initial_view_state={'longitude': -122.42060000000001, 'latitude': 37.7543, 'zoom': 11})
map_

Decision Points

1. Best way to handle non arrow layers. Should we have new classes for non arrow layers that dont include fields like table or should we be extending existing classes and setting table to null/None
2. What parameters should we include for both layers?

[kylebarron]

This looks awesome! Thanks!

1. Best way to handle non arrow layers. Should we have new classes for non arrow layers that dont include fields like table or should we be extending existing classes and setting table to null/None

I'm not 100% sure yet, but at first glance I'd think to have another class BaseArrowLayer (or maybe an ArrowMixin?) that's a subclass of BaseLayer and adds the table, from_geopandas, and _rows_per_chunk traits/methods. Because everything other than those is defined on deck's base Layer class, and should be common for all deck layers