Adds script to update date expressions

[helrond]

Adds a script which will replace unwanted strings in date expression fields with standardized terms, or remove other strings entirely. I suspect this can be refactored substantially (all of the various functions to replace/remove are pretty similar) but let's see if it works as intended first.

[a-berish]

@helrond thanks this looks great! Can we add "circa" [lowercase]?

[helrond]

@a-berish yes but...isn't that the string we want to change the other variants to?

[a-berish]

YES! my bad. This is awesome thank you