Engineers healing Shields mod

There was a discussion on another thread about letting Engineers heal shields. I have implemented this, and committed it to cvs. If individual server admins do not want the ability, they can always leave it out of the UT2004RPG.ini file, but some will want.

Changes are:

New ability AbilityShieldHealing that only Engineers can buy. Allows them to heal shields with the Engineer Link gun. 3 levels, each level increases the xp returned (from 1% to 3%). Increase in level also increases healing rate.

xp is rewarded based upon healabledamage, as also used by medic weapons. This is reasonable as I believe shield damage goes into healable damage

New ability AbilityEngineerAwareness to allow Engineers to see the shields. Implementation based upon the medicawareness class

Note that the shield max for a player is not replicated to the other players, so the awareness healing bar has to assume a max of 150.
Note that the link alt fire will not lock on to a person whose shield is being healed.
Note also that if the target has a link gun, the fire will not heal shields but will just go into normal linked fire mode. It would be too exploitable to have a linked persons shield being regenerated. I believe (but may be wrong) the same applies to a medic link gun.

This is a first draft of the ability, to see how it goes.