Ignore pseudo-system objects in table list

These objects are created by turning on replication and they have column types (sysname, xml) that are not supported by Doctrine. 

According to Microsoft's support, these are "'pseudo-system' object[s]" that appear in the User Table type instead of the System Table type.

https://social.msdn.microsoft.com/Forums/sqlserver/en-US/135ec547-2214-4da3-bd42-5c458759e144/sysobjectscategory

This issue is very similar to http://www.doctrine-project.org/jira/browse/DBAL-114 so I handled it in the same section of the code as the fix for that issue.