Make toolshed update notification only appear if user has used an updated tool

[Tom Goddard]

In ticket #7123 Zach was interested in putting an updated version of the Basic Actions tool on the toolshed. This would cause everyone to be notified for this update even though almost none of our users use that tool. Also the users will not know whether this update is relevant to them.

I think two improvements are needed so that tool updates put on Toolshed do more good than harm. First the update notification should not appear if the tools with updates have never been used by the user. Second there should be a description of what fix was made available in the updates notification tool, for instance, for the #7123 Basic Actions fix it should say "Fixes an error saving sessions when the Basic Actions tools is in use."