Remove rd_leaderboard_enabled from some challenges' txt files

This allows to disable leaderboards in multichallenge.

For dc4-fight_and_flight make the airlock disappear right after hack to make map more interesting to replay

Add ASBI RNG2 and C2 challenges by request

Cleanup code and refactor

Prevent RNG barrels, aliens and other stuff spawned near mission start on some maps. Thanks to jhheight for the fix.

For ASBI WB RNG C2:
Add an experimental feature, activating adrenline gives a 2 second shield around the marine which activated it. By jhheight.
The code for this resides in ASBI Elite challenge. So it is required to be installed for this feature to work.

Make assault rifles secondary fire(grenade) do same damage as hand grenades. Able to kill a shieldbug

Remove barrels from ASBI RNG3 and C2.
ASBI WB RNG3 and C2 still have barrels.

Added ASBI WB RNG4 and ASBI RNG3(without WB)

Make yellow barrels aimable(thanks to Ben Lubar for the hint)