SLA commitments new tables

The following tables are added.

Table 1. New tables
Display Name [table name] Description
Service Offering SLA [service_offering_sla] Stores SLA definitions that apply only to service offerings. Extends contract_sla.
Service Offering SLA Results [service_sla_result] Stores the SLA result calculations (daily, weekly, monthly, annual) for each service offering and each service commitment of type SLA.