Fixes CORE-1987 "mvn liquibase:diff" does not find any differences between databases

Fix empty schemaComparison
Bug fix CORE-1745
Index.equals() method had missing "!" in instanceof check
DVONE-1943 HOTFIX: Liquibase: ANYDATA datatype setting length in Snapshot
Better support for extensions that define their own extension attributes
CORE-2032 Snapshot incorrectly including clob/blob sizes on diff
CORE-1925 liquibase scripts can not represent clustered indexes

Don't include clustered state as part of the index identification
Merge branch 'CORE-1925_primary_key_diff_problem'
Merge pull request #309 from mrorat/CORE-1745-afterColumn_not_working_in_MySQL

Bug fix CORE-1745
Merge pull request #291 from deniedboarding/CORE-1987

Fixes CORE-1987