Exclusively virtual contests

[aurpine]

A new type of contests that allow only virtual participation for on-site and/or live contests held by other organizations (CCC, ECOO, COCI, etc.). This feature will allow users to simulate contests not hosted on DMOJ. As there is no live participation, these contests may require a new categorization (tab).

[WallE256]

Instead of implementing this, we would be better off implementing legit Virtual Contests made by users. Something site-site, which would let the user make problem sets and define start time etc. Design choices can be made later.

[Xyene]

Wouldn't play well with #68, and would make private organizations rather underpowered.

[Phoenix1369]

UVaOJ has something similar. Allows anyone to fully use and appreciate their extensive problemsets. Being able to pull problems from a set to emulate a contest is a wonderful feature. Alternatively, users can simply time themselves (since VC's don't count for anything anyway) without this feature, bypassing private organizations entirely.