Missile lock-on ability and indicator

[IvanSanchez]

Allow missile weapons to lock onto targets with a high enough sensor fingerprint (see #14), or on targets scanned by the Sci console. It should be impossible to lock onto "cloaked" ships, or ships too far away, or ships not scanned by Sci.

If the weapons console is targeting a enemy vessel, display an indicator as to whether a missile can or cannot lock onto that target.

Locking the missile weapons onto a target should take a few seconds (because the sensor fingerprint is being synchronized with the missile sensor pack and technobabble technobabble technobabble technobabble). Blinky "lock" indicator = good.