Add ipyleaflet representation

[banesullivan]

A first pass at adding an _ipython_display_ repr to visualize a tile source in Jupyter dynamically

resolves #1059

I'm having a bit of trouble getting this to work consistently for non-geospatial tile sources

This adds a new rest.py module which is leveraged to launch a minimal tile server for a TileSource using a tornado web server (the same web server Jupyter uses, thus requiring no extra dependencies).

The TileLayer creation is abstracted in getIpyleafletTileLayer() so that users can build the tile layer more easily and/or create custom maps.

import large_image

path = 'oahu-dense.tiff'

source = large_image.open(
    path,
    encoding="PNG",
    projection="EPSG:3857",
)
source

from ipyleaflet import Map

t = source.getIpyleafletTileLayer(attribution="My tile source!!")

m = Map(center=source.getCenter(srs="EPSG:4326"))
m.add_layer(t)
m

Potential remaining tasks

• Add testing
• Figure out why the tornado enpoints only work in JupyterLab and break classic notebook. Perhaps switch to using a background thread
• Verify orientation of medical/non-geo images

[manthey]

I like where this is heading. I'm vacillating on where some of this code should be located -- I half feel it should be in an "IPyLeafletMixin" class that would be added to the TileSource class so that it can live in a separate file.

[banesullivan]

@manthey, I copied this from https://gist.github.com/manthey/a66f69ae84dc59bbd54c2fbbb1c8844f and I'm not seeing the XY reversal issues mentioned in your comments (or am I??). I think this projection generally works, though we could probably improve it to address the following issues I do see (for non-geospatial):

1. Map is centered on top-left corner of image
2. Bounds of map do not match bounds of image
3. Some zoom levels yield "edge"/"border" tiles ... not sure how best to describe these, but I can provide screenshots where black tiles outside the bounds of the image are generated/shown
4. Zoom level 0 does not show the full image in the frame
5. Max zoom level is not working

[banesullivan]

CI is passing tests but codecov client is failing.

@manthey, this is ready for another review

[banesullivan]

@zachmullen and I are experiencing issues where the tornado endpoints here are breaking Classic Notebook, but this works fin in JupyterLab

[banesullivan]

@manthey, this is ready for review. There are some quirks and known issues, but I think this is at a point where it is highly valuable/useful.

1. This does not work in Classic Notebook, only JupyterLab. We may have to switch to using FastAPI over Tornado for Classic Notebook, but I don't think as many people still use Classic Notebook
2. See the inline comment above about potential improvements to the map/projection
3. Testing is just a smoke test to ensure these functions run and don't error (requests are not made)

[manthey]

Let's merge this and refine it in future PRs.

[manthey]

Let's make an issue to revisit the coordinate system of non-geospatial data.