Initial work on PHOENIX-1098 to implement DROP TABLE ... CASCADE. This work a) changes the scan on SYSTEM.CATALOG from a Region to a Table Scan in MetadataEndpointImpl.java b) Allows tables with child views to be dropped if CASCADE is specified and if all the views are on a single region c) If we detect that views span multiple regions we revert to the old behavior of disallowing the DROP TABLE regardless of whether CASCADE was specified.