Improve parsing config XML in AZFP files

[leewujung]

Currently only a subset of variables are parsed from the AZFP XML files. These are the ones that were parsed in the reference Matlab code from the manufacturer ASL Env Sci.

We recently found that in order to encode a unique channel identifier, it would be the best to use the field Frequency Number in the AZFP XML file. However, the current simplistic XML parsing function does not support that. Let's take this chance to improve the robustness of this XML parsing, and also to include the variable units which were not included in the current parser.

For needing a unique channel identifier, see #566, which is addressed by #657.

This is similar to #468.

Tasks

• improve robustness of AZFP XML parser, using something like lxml
• improve AZFP XML parser to include all config variables
• include variable units in the XML file to parser and store accordingly in the set_groups methods

[emiliom]

The first two tasks are addressed in #1151.

I think the third task, "include variable units in the XML file to parser and store accordingly in the set_groups methods", was partly addressed in v0.8.0/0.8.1. Other aspects related to it will be addressed via #1171.

[praneethratna]

Closing, since this was fixed in #1182.

[emiliom]

I've checked off the third task (units), since it was still unchecked. See my note above, #659 (comment)