Feat/col modify row date timestamp

[jamiemonksuk]

This modification allows us to use values from the item row inside col modifiers. It allows for conditional modification and broadens the scope of use.

The use case is needing to edit a date time based on a timezone one a row-by-row basis for Maniax, whose venues span multiple timezones. This has been bodge solved in other places on this repo and I'll amend to use this also in those cases if we put it in.

We'll need to update the Users module to update ColModifierLookupUser in line with this..

I started doing some format fixing but realised there was a lot to do so I left that for now!

I'm open to suggestions if anyone has a better idea :)

[gwillz]

Just to quickly add, I can't say how many of our sites do have custom col modifiers. Worth noting that none of them are on version 3.2 and will need a fair bit of refactoring anyway in order to upgrade - so we can just add this to the list.