Converted to a maven project
Added Metrics as maven dependency, removed embedded Metrics class

Cleaned up formatting
Refactoring lots of onEnable into smaller methods

Encapsulated log variable in DkabotShop
Refactored Sellers and Buyers into their own command package, renamed to reflect they're CommandExecutors
Refactored everything into an appropriately-named namespace

Renamed JPA Entity classes to reflect they are JPA entities
Renamed ShopInfo and History to reflect that they are CommandExecutors