add SFT-vs-output timestamp check to gridsearch, and fix bug in _get_list_of_matching_sfts

Another infrastructure issue: GridSearch doesn't notice when SFTs have been updated. This just ports the check from MCMC, but along the way I noticed it had a bug for single-string path patterns.

-ported check from MCMC search
-bug: for single-str SFT path, glob list comprehension
  was trying every single character

(I hope multiple merge requests don't cause headaches through gitlab...? Let me know if you prefer patches instead.)

mentioned in commit eb65af5d

merged