feat: added new calc flag Calc::CALCULATION_COMPLETE -> pricaefactor are able to set a product price, now

feat: user currency -> the user can now have his own currency, so he can use the exchange rate to display the price in his currency.

feat: extends main comments object -> import and sort methods; the main erp process can return the complete history of all erp objects

refactor: started process class -> represented a complete erp process (invoice, transaction, order etc)