Component property of type date is stored in locale-specific date format

A component parameter of type java.util.Date show a date picker in the component properties box. However, the string value that is stored depends on the currently selected CMS locale (i.e. the 'language' in the login box). This means that the same date can potentially be stored in many different formats, which makes it very tricky to convert it back to a real java.util.Date in the HstComponent.

Steps to reproduce:
1. add a component property of type date to a drag-droppable component (see for example the steps in HSTTWO-2023)
2. login to the CMS with the Dutch language selected
3. open the page with that component in the channel manager
4. select 'Wijzig Template'
5. drag-drop the changed component
6. select the component to show the properties box
7. pick a new date value

Expected result: the date value is stored in a locale-independent format
Actual result: the date is stored in the Dutch format (dd-mm-yyyy)