Py38 mpl313 [WIP do not merge yet]

[alexji]

It's taken a few years, but I've now successfully ported SMHR to python 3. It uses pyside2/Qt5 and updated matplotlib libraries. This means it is now installable using conda libraries. It also appears to work with Big Sur/M1 macs. Since the Python 2 version of SMHR is now actually impossible to install, I suggest having this as the master branch.

I've been using this version exclusively for a month or two now, and it seems to be working fine; maybe it's a bit slower than the original, and with a few GUI glitches, but nothing preventing functionality. It has been installed on a few students' computers (Linux and M1) and they use it successfully.

It also includes my latest and greatest keyboard shortcuts for the Line Measurements tab that greatly speed up the process (using j/k to scroll between lines, space to check/uncheck, F to flag/unflag while you are clicked into the spectrum plot). Possible concerns:

• This is the refactor-scatterplot GUI version, which was never merged to the master branch. However, I think this refactoring and new GUI is better than before.
• things are mostly backwards compatible with previous SMHR files, though there are occasionally glitches with strings as dictionary keys. I have patched these in hacky ways as they arise, but I expect there are corners where I have not fixed that yet.
• occasionally things get buggy with hiding/unhiding checked lines. I don't think this is due to the python 3 port, but not sure.

Important to dos still that shouldn't prevent the PR:

• the RV and normalization GUIs need refactoring (especially so they update cleanly upon loading new files)
• The layout is terrible in Linux
• better default YAML files and better new session startup (most of this is still in the GUI and this causes bugs)
  • there needs to be more yelling when isotopes are not loaded properly.

[alexji]

OOPS the big problem right now is I accidentally merged the RPA version into the main SMHR branch on github (instead of vice-versa). This needs to be undone since I like the version we had previously.

[alexji]

After a few months of continuing to work with this, it seems like it is stable (or at least much more so than the python 2 version). So we are biting the bullet and merging this into master.