Explosive handling

This pull request is in regard to https://github.com/KoffeinFlummi/AGM/issues/426

This initial PR comes with a couple issues:
* All placement objects for explosives are the multi meter (due to it having physics and it's fairly usable)
* Still makes use of the action menu for approving of placement or cancelling placement of an explosive (Place, Attach To, Cancel)
* If you directly pickup a clacker object (instead of going through the gear menu) it doesn't get the clacker explosives

It would still require testing and so forth but it is essentially the same as https://www.youtube.com/watch?v=x0-8JN-Hbqc in terms of the placement (not the IED creation screen).

![2014-07-10_00003](https://cloud.githubusercontent.com/assets/383331/3545269/03d657f2-0875-11e4-9a1c-9989f59ed8d2.jpg)
![2014-07-10_00004](https://cloud.githubusercontent.com/assets/383331/3545272/0dce0372-0875-11e4-9fa7-70612e385134.jpg)
Selecting which explosive to place, the UI is already better with it actually changing the text of the buttons so the player would know what is happening better.