Update To Modern Stack [unaccounted for]

[rhodges]

Bring the stack, including 'marineplanner-core' and 'ucsrb' up to date to run on:

• Ubuntu 20.04 LTS
• Python 3.9
• Django 3.2 (when released 4/21)
• OpenLayers 6+

[rhodges]

Current Dev code now supports:

• Ubuntu 20.04
• Python 3.8 (close!)
• Django 2.2 (latest LTS for now)

I don't expect and upgrade from Python 3.8 to 3.9 to cause many problems.

I DO expect Django 2.2 to 3.x will have some hiccups, but FAR less than 1.x to 2.x.