Granular testing balance using votes

This has the following benefits over the current solution:

• low risk for admins - they no longer need to worry about alienating their players by forcing changes on them - the players decide whether to test or not
• can test individual changes instead of all at once
• allows testing of competing changes which touch the same cvars (yes, will have to deal with the possibility of players enabling both at the same time - one will have to disable the other)

Once this is merged i will propose the alternative electro and crylink secondary i have in mind, no need to make the MR too complex now.

Also with this, i don't think it's necessary to have an open MR for a proposed change as we do now - it's just one more thing to keep in sync. As an example, we forgot to change linkexplode in testing balance (the file is rewritten anyway with this MR) when we merged that. A forum thread and a vote should be enough.