Updates eng rig path, adds obj sprites

Adds object sprite sheets for tajaran, unathi and skrell hardsuits, where the icons were available (just engineering and syndie hardsuits for now).

Makes engineering hardsuits a subtype of the parent rig type, so it is
now possible to update eng hardsuits without affecting every other
hardsuit type.

(cherry picked from commit 3d9f1754cd6413f2efdd8407aab133dce3cc4729)

Conflicts:
	code/modules/clothing/spacesuits/rig.dm
	maps/tgstation2.dmm