[New Feature] De-hardcode DrainWeapon from vertical/fire

[deathreaperz]

Based on https://www.modenc.renegadeprojects.com/DrainWeapon , this section:

Using DrainWeapon enforces several special cases upon the weapon:

1. Such weapons do not actually fire their projectile or warhead, using it only for targeting purposes.
2. Such weapons are hardcoded to play the "DISKRAY" animation when firing.
3. The engine expects them to be fired vertically downwards from above a building (as when fired by the Floating Disk) and they will hence fail to fire when fired from any other position, or stop firing if the firing unit moves away from a position right above the structure, even if firing was still permitted by their Range. Aircraft cannot fire them either. In essence, this means that you are limited to BalloonHovering JumpJet units to fire such weapons.

It will be nice if we have de-harcoded DrainWeapon that land/naval units can also use. For example:

[Comet]
DrainWeapon=yes (def no)

[CometWH]
Drain.Animation= (def [General]>DrainAnimationType)

With this de-hardcode, I hope it will support ARES' Drain Weapon Options as well from http://ares-developers.github.io/Ares-docs/new/drain.html