IWatchViewer.Watch signature needs to be changed slightly #32

The IWatchViewer.Watch signature needs to be changed from

(string * 'a * Type) -> unit 

to

(string * obj * Type) -> unit

since the current signature makes it difficult for plugin authors to 
dynamically cast the value, of generic type 'a, to a more specific type. As a 
work-around, first statically cast the value to obj, and then dynamically cast 
that to the desired type.

This issue affects FsEeye 2.0.0-beta1.