Integrate Static purchasing model into framework

Move purchasing stuff to single package

Add Discrete PDF

Rename purchasingprofile to purchase

Remove PurchasingProfileBuilder and change names of others to indicate Markovian

Refactor out PurchasingProcesses interface

Fix indentation

refactor purchasing profile builder

Rename purchasing profiles to purchasing models

Collapse purchasing processes, undoing previous work

Integrate Static purchasing model into framework

Add toString to Pair

Add UUID to Product

Fix DiscretePDF so it checks key, not value