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.

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
"Unable to fetch data for %s. Please, try again in a few minutes."

Which kind of brings up the question whether we should have another timeout option :D Note that this is one of the rare occasions where I'm letting a "please" slip inside the message. If you're wondering why - the reason is that we are causing an inconvenience to the user and we are kindly requesting for their patience.