Wrap IOrchardShellEvents into WorkContext

[orchardbot]

@Piedone created:
https://orchard.codeplex.com/workitem/21023

Currently there is no active WorkContext when IOrchardShellEvents events are fired. Thus if you implement this interface and try to use any injectable dependency in it that depends on a WorkContext being present (this could be the case with a simple Work injection) then you'll get errors like this one.

To mitigate this IOrchardShellEvents could be executed in the scope of a short-lived WorkContext.

[orchardbot]

@Piedone commented:

Related: https://orchard.codeplex.com/workitem/20738