Use delete marker instead of null to represent a row deletion in MutationState. This prevents an issue with keeping track of the number of rows correctly and prevents us from having to do an extra contains check when joining two mutations
Additional error checking around ARRAY usage: disallow usage in ORDER BY and non equality comparisions
Rename PTableType.USER to PTableType.TABLE, fix comparison check for ARRAY, support ALTER VIEW|TABLE, check expected table type against actual table type