Apply glow effect for visible enemy clan members

[RoboMWM]

If and only if in line of sight, enable spectral glow when near an enemy clan member.

• Perform world check
• Remove on quit

[RoboMWM]

May be possible to "only color enemy clans" a certain color: https://www.spigotmc.org/threads/api-glowapi-1-9-1-10.128007/page-3#post-1791633

However - since there are more than two clans, it may not make much sense to do this (e.g. Planetside 2 always uses faction-specific color).

[RoboMWM]

Spectral effect used for other things + causes client lag unless using optifine+fast render