VDC resource and datasource, Region Zone data source

[Didainius]

Main

• New Resource: vcd_tm_org_vdc to manage Tenant Manager Org VDCs [VDC resource and datasource, Region Zone data source #1350]
• New Data Source: vcd_tm_org_vdc to read Tenant Manager Org VDCs [VDC resource and datasource, Region Zone data source #1350]
• New Data Source: vcd_tm_region_zone to read Region Zones [VDC resource and datasource, Region Zone data source #1350]

Extra

• The generic type crudConfig is split to have additional type dsCrudConfig specific to data sources. The reason is that in the case where read-only APIs exist, one cannot use crudConfig because the updateDeleter type constraint is not satisfied (because read-only entities do not have Update and Delete methods)
• make testtm-coverage added that will write a coverage file to tm.cover