115 supplying list of SSOIDs to CLI

[astronomerritt]

Fixes #115.

• Added a new command-line argument, -sl, that allows the user to supply the location of a list of SSOIDs. This command-line argument is mutually exclusive with -s and the user must supply one or the other.
• Added validation of this command-line argument to AdlerCLIArguments - to check the file exists.
• Changed adler.py to now iterate over a list of objects. Added a helpful message that prints to the log and lets the user know how far along we are.
• Wrote a function, adler.utilities.readin_utilities.read_in_SSObjectID_file(), that simply reads in the contents of a text file assuming that it consists of a list of SSOIDs, one on each line. Does some basic validation to make sure the input is sensible.
• Wrote unit test for the above function.
• Wrote extra unit tests for AdlerCLIArguments to cover the new argument.

Also:

• As we're now iterating over a list of objects, I have stopped warnings from printing to the terminal (to reduce terminal spam). The warnings print to the logs so they're still readily accessible.
• I removed the unit test that checked to see if warnings were printed to the terminal (as they're not).
• Forgot to add a docstring to my logging function, oops.

If you'd like to test this on the RSP:

>> adler -sl ./tests/data/test_SSOIDs.txt

Review Checklist for Source Code Changes

• Does pip install still work?
• Have you written a unit test for any new functions?
• Do all the units tests run successfully?
• Does adler run successfully on a test set of input files/databases?
• Have you used black on the files you have updated to confirm python programming style guide enforcement?

[jrob93]

Looks good!