Modularize the pdgstaging library

[robyngit]

To eventually support more flexible workflows, the viz-staging package first needs to be broken down into smaller, more flexible classes and functions.

[robyngit]

Changes made thus far while working on this issue have resulted in some performance improvements. The new Grid class takes advantage of the grid's uniform structure to make faster versions of GeoPanda's overlay and sjoin methods. I replaced the GeoPandas.overlay and GeoPandas.sjoin methods in the Tile class with the Grid equivalents. In a small test of staging 15 IWP files, the new methods resulted in staging times that were almost 10% faster overall, and the gains in speed were relative to the filesize (i.e. the new methods saved the most time for the largest files).

Since a 10% improvement in performance might help with our current work on processing the IWP dataset, I've merged all of the changes made at this point into the develop branch. These changes DO NOT impact the API. In other words, everything should run as it did before, except with better staging times (FYI: @KastanDay)

[robyngit]

Just met with Chunli & others about her ArcticDEM change detection data, which provides another use case to think about while working on making this workflow more modular and flexible

Here are some details about the data & requirements:

• The data comprises 2km x 2km GeoTiff tiles that cover the arctic
• These tiles overlap somewhat, and we should display data from just one of the tiles in the areas of overlap (rather than taking some aggregate of pixels at the same location)
• The best way to determine which tile is preferred in areas of overlap is to read in data from another set of 2km x 2km tiles: for example, there is another layer of tiles that shows the # of DEMs used to calculate the result for each pixel. We could choose the tile with the most DEMs overall.
• The workflow will involve deduplicating areas of overlap, as described above, in addition to essentially re-tiling the data to correspond with an OGC Two Dimensional Tile Matrix Set.

[robyngit]

The new Grid class can be used independently of the staging step, making the library more modular than before. We can open up new issues that layout the specific tasks to be completed if we decide more modularization is needed.