Bugfix - Inventory position

Hey everyone,

I've fixed a bug in the source code concerning the inventory position. The inventory worked fine on the default position. But  if you moved it, the placement of the items in it looked weird. That has been fixed now, but there are two things I need to explain:

1. I strongly recommend moving the TextureRect and SubViewportContainer nodes instead of the Inventory root node. The reason is that the inventory was designed to be an extendable fullscreen menu. That's how the inventory in Diablo etc. works, as you are still able to do inventory actions outside of the inventory UI, like dropping an item. 

2. Also do keep in mind that those two nodes should be positioned inside the grid defined by TILE_SIZE to have proper alignment.

By following these instructions you will not encounter this bug again with the updated source files (hopefully).

That's it for this update. Until next time, bye bye.