Supporting of "Classify as" option

[GeorgeAlexandria]

Will be good to add possibility to classify item as on of others or just don't classify it.
This opens way to classify items or ignore them classifications that already classified in the Visual Studio, look at the issue #24.

Also, need to come up with a design which will marks items in the cycle with the current selection in the "Classify as" option or as another posibility just hide items in"Classify as" which build cycle with the current item.

[GeorgeAlexandria]

After a little investigation I think that a graph (cycle dependensies) should be visualized by MSAGL. But currently I'm not sure that this graph will fit in the CoCo option page and I also don't see a good design that will compose the choosing "classify as" item and the showing cycle dependencies which are building during the choise.
Decline selection of "classify as" item which build cycle dependencies doesn't help to understand which nodes are build this cycle and how much ways are exist to break cycle.

So I decide to postponed on later this issue, hoping that a good design will found for it.

UPD: moved the part about of disabling classification into the separate issue #43