title: Liquibase diff gives constraint error
body: <p>I get this error when I try with both command line and Maven invocations:</p>
  
  <pre><code>Diff Results:
  Unexpected error running Liquibase: liquibase.exception.DatabaseException: liquibase.exception.DatabaseException: Unknown constraint type: 3
  </code></pre>
  
  <p>This is using a SQL Server DB. Created both the reference and target using liquibase:update.</p>
  
  <p>Properties:</p>
  
  <pre><code>driver=com.microsoft.sqlserver.jdbc.SQLServerDriver
  url=jdbc:sqlserver://localhost:11433;databaseName=DB 
  username=user
  password=pass
  referenceUrl=jdbc:sqlserver://localhost:11433;databaseName=DBRef
  referenceUsername=user
  referencePassword=pass
  </code></pre>