Enhance SRU tools

[william-billaud]

As stated in #34

Ah apologies, I thought serialise_record_column_values was from this file and did some value conversion (the AppId, UserId, ts stuff), but that's not the case.

this is not done in repr either, but I can add it (but maybe in another PR).

Yes I only just now noticed this. That would be appreciated and can be a separate PR. Thanks!

[MrIridescent]

Hi! I'd like to take a look at this. I'm new to the project but I've fixed similar issues before. I'll submit a PR shortly.