Added the preserveGetParameters() method to Form
Merge branch 'hotfix/3.0.2' into develop
Validators must pass through the widget value for the model

The widget value must not be changed by default, as if the
form has an error, we don’t want the timestamp to appear.
However, this is an API change so needs to go into 3.1
Convert to timestamp before custom save_callback so they get the tstamp value
Added ModelData generator
Added ModelData token generator
CS
Allow custom validator classes
Implemented a simple mandatory-on validator
Mandatory check should obviously only be applied when the value is not empty
Merge branch 'feature/modeldata' into develop
We do not need to check widgets, it could be correct to be empty
Date conversion did not correctly handle datim
Mark state clean as soon as widgets are generated
Added helper methods to get current form configuration
Use methods internally
Required attribute should be set when generating widgets
No need to create widgets if we’re not submitted
Initialize status variables when generating/validating the form
Exceptions in validators should cancel the validation loop