inventory create/apply template buttons

This change adds create template and apply template buttons to the soldier inventory screen, visible only during the initial loadout configuration (i.e. when accessed from the base craft inventory button or the initial inventory screen when starting a mission).  When the create template button is clicked, the equipment layout for the current unit is copied and saved.  When another unit is selected and the apply template button is clicked, the saved equipment layout is applied to the current unit, using items from the ground.  If there aren't enough of any relevant items on the ground, the corresponding slot is left empty, but the template is followed as closely as possible with the available items.

The new buttons and functionality are not available during a mission, when TU management and lack of a common "ground tile" would make this feature awkward.

Screenshots:
Before the create template button is pressed: 
![before_copy](https://cloud.githubusercontent.com/assets/977482/2606279/22c87a60-bb4e-11e3-8d5c-4cd3569eea56.jpg)

After the create template button is pressed (notice the visible change in the icons to indicate the changed state): 
![after_copy](https://cloud.githubusercontent.com/assets/977482/2606282/29984866-bb4e-11e3-9e62-36d164060699.jpg)

Another unit with different equipment, before the apply template button is pressed: 
![before_paste](https://cloud.githubusercontent.com/assets/977482/2606287/33d3350c-bb4e-11e3-8b73-ad28bf890b0a.jpg)

After the apply template button is pressed; notice that previously-equipped items that were not in the template have been moved to the ground: 
![after_paste](https://cloud.githubusercontent.com/assets/977482/2606289/390dea9e-bb4e-11e3-8a09-fa0891ccb9b2.jpg)

Other notes:
- If the apply button is pressed before the create button is ever pressed, all items on the current unit will be dropped on the ground
- hotkeys for the new buttons are configurable and are 'c' for create template and 'v' for apply template by default
- clicking the apply button will give some audio feedback that the inventory has been modified (uses the same sound as when you click on an item or drop an item in a slot)
- if an item with ammo is picked up, the ammo display will appear in front of the buttons, clipping them: 
![clipping](https://cloud.githubusercontent.com/assets/977482/2606332/ac344afe-bb4e-11e3-9fd8-cf6995109e56.jpg)
- If there aren't enough items on the ground to satisfy the template, a warning message is flashed on the screen: 
![after_paste_not_enough_equipment](https://cloud.githubusercontent.com/assets/977482/2606303/5bf97dd4-bb4e-11e3-8fd2-8ee3294d9c8e.jpg)