Support for Joda Time Library

This resolves the problem of filtering Joda Time Library objects:
* http://gpc.github.io/grails-joda-time/

Parsing of Data/Time/Duration/etc. objects:
* Automatically by Joda convention
** http://joda-time.sourceforge.net/apidocs/org/joda/time/convert/ConverterManager.html
** Therefore support for all class types
* Or by grails date picker properties
** propName_year, propName_month, propName_hour, propName_minute

Consider resolving of:
* http://jira.grails.org/browse/GPFILTERPANE-85

Documentation:
* I didn't put the documentation about this into the respective part. I don't know if you should create a separate page which would speak about java.util.Date and Joda Time filtering, implementation of date picker, etc.

Tests:
* Also not implemented...