Target list cleanup - Githubissues

Describe your changes

TargetList prototype (and implementation) cleanup.

Fixes inconsistently documented luminosity units. EXOSIMS stores target luminosity in L_sun (linear, not log).
Adding new attribute required_catalog_atts for use in the nan_filter (instead of filtering for nans in any attribute)
Offloading all fillPhotometryVals functionality to package MeanStars (and adding it as a dependency)
Spectral types are now required to be matched and targets without known type are discarded. Spec string is overwritten with well-formatted string for easier downstream lookups.
populate_targets now only does just that - other steps are moved back into the init.
Adding new method defining catalog attributes for easier overloading.
Removing urllib3 dependence, updating IPAC querying for aliases and fixing alias caching system. These queries take a while, so adding a base list (all EXOCAT1 targets) to be distributed with the code.

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Checklist before requesting a review
[x] I have verified that all unit tests pass in a clean virtual environment and added new unit tests, as needed
[x] I have run e2eTests and added new test scripts, as needed
[x] I have verified that all docstrings are properly formatted and added new documentation, as needed
[x] I have Blackened my code