Add primary key to version table
Fix handling of default value
Fix index update

* Old indexes are now dropped
* New indexes are now properly updated if name of constraint has changed
Key fields specified should also use backtick quote

This prevents errors with strange column names such as 'int1'
Merge remote-tracking branch 'origin/more_flexible_code_generation'
Merge remote-tracking branch 'origin/add_primary_key_to_version_table'
Merge remote-tracking branch 'origin/fix_default_values'
Merge remote-tracking branch 'origin/fix_index_removal'