Refactor away from PDF language

[Sparks29032]

Closes#236

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.92%. Comparing base (de41950) to head (d928a81).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@ Coverage Diff @@## main #261 +/- ##
=======================================
Coverage 99.92% 99.92% =======================================
Files 24 24 Lines 1398 1398 =======================================
Hits 1397 1397 Misses 1 1 

Files with missing lines	Coverage Δ
tests/test_morphapp.py	100.00% <100.00%> (ø)
tests/test_morphchain.py	100.00% <100.00%> (ø)
tests/test_morphio.py	100.00% <100.00%> (ø)
tests/test_morphrgrid.py	100.00% <100.00%> (ø)
tests/test_refine.py	100.00% <ø> (ø)

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[sbillinge]

@Sparks29032 this is ready for merge but unfortunately it is conflicted with the earlier merge i did of the citation.cff file

[Sparks29032]

@sbillinge Should be fixed