Fix grace period happening during Waiting for Players

[woisalreadytaken]

The plugin restyling (#47) changed a lot of things, but an issue it brought is that with a change to the Round State enum struct, it skips over a step and sees the waiting for players period as an actual round, and this breaks a couple of things:

• The first round skip immunity/mechanic is ignored and will catch players after a set amount of time during waiting for players and will force undeserving players to the infected team in the first round.
• As a result, the anti-exploiting feature introduced with PR #44 will also be active during waiting for players, making everyone (except the very first player) unable to join either team until the emergency 45 sec grace period timer ends, confusing a lot of people.

This PR simply re-adds the waiting for players step as a round state.

[haxtonsale]

Use TF2_OnWaitingForPlayersStart and TF2_OnWaitingForPlayersEnd?

[woisalreadytaken]

ok did that, the events don't look like they work anyway