Update Dockerfiles to build with python3, update urlparse import for …

[ctcudd]

Update Dockerfiles to build with python3, update urlparse import for python3 and move to compatible/more recent version of requests library.

Issue #, if available:

• Incompatible with Ubuntu:20.20 #25

Description of changes:

• Python2 is no longer configured as the default with Ubuntu and this is causing the current Docker build to fail. To resolve this I've updated the build to use python3 (similar to this PR)
• The location of the urlparse method was changed in Python3, I've updated the import statement in mysfits_like.py with the new location (see https://stackoverflow.com/questions/29358403/no-module-named-urllib-parse-how-should-i-install-it)
• dependabot is correct, an updated version of the requests library is required for the like-service to function properly

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[MitchyBAwesome]

This looks good and seems to address most of the dependency challenges reported recently. @amui @hub714 Any other observations before merging?

[hub714]

This looks good to me and is also what needs to be changed on the main MAD workshop too.

[amui]

Looks good, some tweaks to readme are needed, but will do that separately.