Features: asw_door: add DelayBeforeClose input

[Kitsune44]

Add a new input DelayBeforeClose to the asw_door entity.

This input specifies the number of seconds after a door has opened
before it automatically closes. Setting the value to -1 disables
automatic closing. The input is implemented in CBasePropDoor in code
and available in Hammer for asw_door entities.

Checklist:

• Code changes implemented
• Tests / Verification

done