lib/log/NullHandler should be removed and be replaced with logging.NullHandler

[jauy123]

lib/log/NullHandler should be deprecated. The standard library in 3.1 introduced it's own version of NullHandler (coincidentally with the same name). Therefore, MDAnalysis lib.log.NullHandler should be removed and be replaced with the standard library equivalent, logging.NullHandler.

Found while working on issue #5357 and PR #5367. I will remove this in PR #5367 rather than make it separate PR.

[jauy123]

This make me curious. Is lib/log.py older than python 3.0?

[orbeckst]

MDAnalysis started with Python 2.3 or earlier (see CHANGELOG). There's some historical crud in there without a doubt. By all means, clean it up :-).