Add tool to create a heat map from an occurrence csv file

[cjgrady]

The first version should create a tiff with counts of the number of occurrences found in each cell. Future iterations may create geojson instead so that we can use hexagons or other shapes for the cells as well as add some additional information like the number of points in each cell as well as the number of species. We could also create something like a PAM where we have columns for each species and the value is the number of records found in each cell, or perhaps even model values for smaller datasets.

First version inputs:

• Occurrence csv filename
• Species or group header key in the csv
• X header key in the csv
• Y header key in the csv
• Occurrence data EPSG code (we'll assume that it is consistent for all records for now at least)
• Output heat map filename
• Heat map EPSG code
• Heat map bounding box values
• Heat map resolution (probably should have option for x and y resolution)
• Heat map nodata value?

[cjgrady]

I have a first version of this script in an lmpy branch but I'll move it to lmtools. I think that it may end up in lmpy in the end if it is robust enough and more widely useful but it makes sense that it would just be for us for now.

[cjgrady]

This is included in lmpy now