Final update to inventory.cpp

This SHOULD be the final update to the inventory file; everything is working properly and is ready for integration.
Final update to inventory.h

The finalized header for inventory.cpp. Only additions are the threshold functions.
Merge 'heroque' into 'unstable'
Merge branch 'unstable' of https://github.com/CS-240-Group-2/Big-M.A.C into unstable