Convert ALL dates sent to the backend to UTC

After some "stress" testing of the site, it was found that there were super jank bugs relating to the dates. These were things such as:

Off by ones
Inconsistent display between admin and user view
Weird error messages that were hard to debug

Which led to the work in #463 #421 #465

Instead to combat this it was decided to stop using Date where possible on the back end, and make sure that all "dates" are "normalised" to the UTC 00:00:00 before being sent to the backend.

Big change that was verified to not break anything was to get rid of the DatesToDateRange function on the backend, in favour of a Timestamp alternative.

No functionality was broken, however some tests needed to be re-written to accomodate for the new changes - hopefully the current coverage is enough

Would close #431 `

Have also updated the wiki with https://github.com/UoaWDCC/uasc-web/wiki/Backend-Architecture#note-on-dates and https://github.com/UoaWDCC/uasc-web/wiki/Frontend-Architecture#dateutils

UoaWDCC / uasc-web

Convert ALL dates sent to the backend to UTC #466