FIX: Improve strictness when parsing TDB FUNCTION and PARAMETER lines

[bocklund]

Checklist

• The documentation examples have been regenerated if the Jupyter notebooks in the examples/ have changed. To regenerate the documentation examples, run jupyter nbconvert --to rst --output-dir=docs/examples examples/*.ipynb from the top level directory)
• If any dependencies have changed, the changes are reflected in the
  • setup.py
  • environment-dev.yml

This PR makes the TDB parser more strict by requiring that PARAMETER and FUNCTION lines are terminated by an optional-suppressed reference key and a line end. This fixes behavior where the parser would silently consume all TDB content until the next line terminator (!) for these two commands once the func_expr grammar was successfully parsed.

• FUNCTION and PARAMETER pyparsing grammars are updated to include through the line ending, if the parsed function expression and reference key is not following by a line ending, a ParseException is now raised.
• A failing test based on unexpected behavior of G^ref when temperature range is set? #307 was created and merging this will close unexpected behavior of G^ref when temperature range is set? #307
• Before this change, I had 522 databases that were known to be parsed successfully pycalphad. After making the change, all 522 still parsed successfully. The only TDB that did not parse correctly was the ALNIPT_TDB database in our test suite, which had references of REF: 0, which I changed to REF0 (I also verified that Thermo-Calc 2020b says that REF: 0 is an invalid reference format in GES6)

[codecov]

Codecov Report

Merging #308 (11908cc) into develop (be40446) will increase coverage by 0.01%.
The diff coverage is 100.00%.

@@             Coverage Diff             @@
##           develop     #308      +/-   ##
===========================================
+ Coverage    86.77%   86.78%   +0.01%     
===========================================
  Files           46       46              
  Lines         4460     4464       +4     
===========================================
+ Hits          3870     3874       +4     
  Misses         590      590              

Impacted Files	Coverage Δ
pycalphad/io/tdb.py	87.89% <ø> (ø)
pycalphad/tests/datasets.py	100.00% <ø> (ø)
pycalphad/tests/test_database.py	100.00% <100.00%> (ø)

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[bocklund]

The failing Ubuntu Python 3.9 test is caused by an error uploading coverage to codecov. The test suite itself passed.