Daravind/Catalog metrics storage

CatalogMetricsStorage

1) Added support to Metrics Service to store metrics in a Catalog
2) CatalogMetricsStorage only writes to Catalog from 1 (background) thread by using a ConcurrentQueue
3) Also, using 'ShouldUseDBAndCatalog' setting, metrics may be written both to DB and Catalog
4) Following settings are supported as well
     i) IsLocalCatalog - uses filesystem
     ii) CatalogPageSize and CatalogItemPackageStatsCount to determine how the Catalog is built
This should be two separate flags.  One for using DB and one for using Catalog.  That allows us to turn them on/off independently.