Merge pull request #27 from kuceram/filter-by-subclass-attributes

Filter by subclass attributes
Merge pull request #26 from kuceram/filter-by-class

Build is failing, going to pull and check if I can fix it.
Adding pull requests 26 and 27
Update FilterPaneUtils.groovy

Fixed another error that affects properties beginning with op
Merge pull request #28 from stenix71/patch-5

Update FilterPaneUtils.groovy
Merging fix for op named filters
Merge branch 'master' of github.com:Grails-Plugin-Consortium/grails-filterpane into develop
Fix for class property resolution, class for super classes is handled as a string to criteria query whereas custom Class types are handled by Class attribute