update l2d_tiles

[matthewhanson]

l2d_tiles operates differently than the other scripts.

For now it's been moved out of scripts directory. It currently works using hardcoded directory patterns (Polygon_???utm???), and operates on a collection of directories.

See tutorial in docs for how other scripts work. To be consistent l2d_tiles should:

• operate on a single set of LAS files at a time
• provide it a directory, it creates output shapfile using all .las files in that directory
• output to a shapefile, default to tiles.shp in current directory

[matthewhanson]

l2d_tiles is better implemented using the pdal command
pdal info --boundary lasfile

which will calculate the hex surface surrounding all the points. l2d_tiles, or similar utility should get the boundary for each tile and combine them all into shapefile with an attribute giving the filename.