* CircleInfo.cs:
* CircleInfoCollection.cs: cleans imports
* CircleManager.cs: implements a circle manager
* CircleProvider.cs: Defines a default Circle provider
* EventPub.cs:
* CalendarController.cs: refactoring
* CircleController.cs: implements with default circle provider
* FrontOfficeController.cs: throws descriptive exception message at
searching for a catalog
* Catalog.aspx: Fixes links on product categories
* ProductCategory.aspx: Fixes links on products
* YavscModel.csproj: Includes Circle provider definitions
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