In testing it was discovered that a separate resource_pools
tables was not required. Instead the resource-providers table
itself could provide that and any given provider could provide
multiple resources classes, associated via the inventories
table.
Therefore, this adds 'name', 'generation', and 'can_host' columns
to resource_providers and changes an allocations index to add the
'used' column.
A 'resource_providers_aggregates' table is added to associate a
resource provider with an aggregate.
A unique constraint is added on the inventories table so that any
resource provider can have only one inventory for any given
resource class.
Change-Id: Ia28be42a75e0977faf9bbc91d1ad9d8661b99230
Partially-Implements: blueprint resource-providers
b70185c72e