Autocrafting system rework about inv.lua

[lewark]

To fix #28, it may be necessary to find a complete solution for the requested item and then queue all of the necessary tasks at once. The current implementation of CraftManager is limited to one recipe per item type so under this restriction the algorithm may be straightforward. However, supporting fallback recipes would remove this simplification.

The items may also need to be marked as reserved somehow so that a second autocrafting task does not interfere with the first. The current system where tasks are added iteratively could be preserved if extra materials that are currently being crafted are counted. However, I wonder if it would be better to solve for the recipe using a recursive function, like how the early versions of this software did, instead of through the task system.

[lewark]

Converted this ticket into an overview of all autocrafting-related issues.