[FTR] Calendaring plugin type and Outlook

* closes #1136
[REF] Many fixes and refactoring in calendaring plugin

* Redo main method for Outlook Task in order to avoid sending twice the request to Outlook
* Added OutlookTaksRegistry
* Renaming many classes and methods.
* Changing User Details page: do not specify 'Plugin preferences' but mix with the others.
* Removing default values from options (because they are site specific)