Add fixes from jump plugin

[allvei]

Adds the following fixes:

• Makes rampsliding much more consistent.
• Fixes +attack2 preventing reloading and firing rockets.
• Fixes rockets not firing if +attack is held for 1 tick.
• Fixes rockets getting desynced with the shooter to remove randomness.

Closes #14

Fix 3 and 4 may need further testing as locally I can't really be sure they work exactly as needed.

[allvei]

@prplnorangesoda why force push? The PR is still open.

[Av3r4ge]

Tested locally, the rocket syncs feel weird to me but I'll test more later. Everything else works perfectly

[allvei]

Best to test p2p next.

[prplnorangesoda]

Merge this before the next playtest