Rework Docker: Python 3 + Remove GDAL

[DavidLemayian]

Description

This PR reworks Docker and how we use Kenya as default app for easier development of the package and possibly smaller docker images.

This also switches to Python 3.

And removes GDAL because we've implemented mapit.

Lastly, we get rid of the hurumap-dashboard image.

Type of change

Please delete options that are not relevant.

• [ ] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [x] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [ ] This change requires a documentation update

Screenshots

N/A

Checklist:

• [x] My code follows the style guidelines of this project
• [x] I have performed a self-review of my own code
• [x] I have commented my code, particularly in hard-to-understand areas
• [x] I have made corresponding changes to the documentation

[DavidLemayian]

@phillipahereza Made it Python3 compatible on this branch - https://github.com/CodeForAfricaLabs/wazimap/tree/feature/python3

[DavidLemayian]

@kilemensi we won't be keeping 2.7 compatibility. I'm not sure why those show up but could you clean them out for me and merge when ready?