Discover when .net 4.0 is not installed and give a proper error message

Fixes http://teampulse.telerik.com/view#item/281235
Merge pull request #587 from Icenium/totev/net40

Discover when .net 4.0 is not installed and give a proper error message
Fix plugins commands

Change platforms property of IPlugin from string[] to Server.DevicePlatform[] type. Add try-catch when fetching data for specific plugin - this way if we fail while fetching data for one of the plugins, information about rest of them will be shown to user. Add test to verify plugins data will be shown correctly when we are unable to get data for one of the plugins.

Change url to MarketPlace to use https instead of http.

Fixes http://teampulse.telerik.com/view#item/280934
http://teampulse.telerik.com/view#item/280394