Upgrade PyLogbook to use REST rather than JPype

This is based on work from @bbielaws in https://gitlab.cern.ch/be-rf-cs/Tools-and-libs/pylb.

I've marked this as a WIP until we are all happy to merge. On my side there are a few places where I'd like to see (and propose) changes before that point, but I figured it was easier to make merge requests against a branch than to write them in an issue.

In order to ease the collaboration, please make merge requests against develop for any changes that are desired to this MR.