UPS follow up fixes

Fixes the issues from that comment over there https://github.com/CleverRaven/Cataclysm-DDA/pull/9652#issuecomment-60331908

> Minor complaint: the UPS can be activated but that doesn't do anything now. Not a dealbreaker but should be fixed before stable. ;-)

Seems to be a general problem, it's the same for the both forges. They have no iuse function, so the game does nothing when invoked. I added a message for that case.

> Not sure if this PR causes it, but wielded powered-items with a UPS conversion installed don't charge. Put it back in main inventory and it charges as expected.

That seems to have been overlooked in eff239b1335b45746f3257d880ba50b17acd0cfd, it needs to check against `maximum_charges` like it does for items in the inventory, fixed.

> Minor quality-of-life issue: tanksuits don't indicate their on/off status at the moment

That's another bug. I've only seen them yellow in the inventory window, that was enough for me. But I added another item suffix for those items that are active, but have no separate active item type. Usually the active item type has the id "foo_on", so it checks whether the item id has the suffix "_on" and if not adds "(active)" to the item name.