Add various `parse` functions

[gallais]

The one function in TParsec.Running is only ever useful to write down
examples but not to actually use it. It'd be nice to have specialised runners
for input String vs. Text and output Maybe a or List a.

[clayrat]

I made a parseMaybe function for internal use which is very similar to parse, only returning Just/Nothing instead of Singleton/Void. Not sure about returning List though. Also what do you mean by Text?

[clayrat]

We currently have parseMaybe, parseType, parseResults and parseResult - do you have any other useful variations in mind, or should we close this?