Some fields are badly displayed when creating the application structure, before saving it, if the default wiki syntax is not XWiki 2.x

Follow this steps to reproduce:

• enable the Plain 1.0 syntax from the Administration and make it the default
• start creating a new AppWithinMinutes application, but stop at the application structure step; it's important to not move forward because the problem doesn't reproduce if the application class is saved;
• drag & drop the Date field

Some wiki syntax is displayed (the include macro) instead of the date input.

The reason is because the property custom displayers (on the application structure step) are rendered using the syntax of the class page loaded from the database. This means that before the class is saved the custom displayers are rendered using the default wiki syntax rather than the syntax of AppWithinMinutes.ClassTemplate. As a consequence, if you drag a Date field before the class is saved the field won't be displayed properly if the default wiki syntax is not XWiki 2.1.