Made egp hud able to be linked to multiple vehicles

Fixes #469
Fixed adv emarker not unlinking entities when they are removed
Made R:concat and T:concat not cause lua errors

... when used on arrays or tables with userdata objects in them (such as
players)

Fixes #449
Made remote uploader display ops and cpu of all E2s (admin only)

This will be useful for admins, to see if an E2 is using a lot of cpu
time.
It is disabled by default, due to potentially using a lot of networking
(if there's a lot of E2s out). To enable it, go to the "Expression 2"
tab of the E2 editor options menu - there's a new checkbox there.
Made remote uploader syncing not send the name of the E2

Saves a lot of net message space