Now with actual consuming!

Today I implemented some string conversions for a later stage and then finally some connection between UI and logic. The result is, you can now consume items from within the inventory!

I should really implement mixing xD
also, I want the submenu to be shown on the item slot it is called upon, that shouldn't be too hard.

changes:
https://github.com/Papiertig0r/Alchemy/commit/59c40642e9dc00f05b94b7c8385801c3600049a9