Add a refresh button to the Project Browser

[mwieder]

The Project Browser annoyingly loses its content regularly. This patch adds a button to the toolbar to refresh the content when it gets messed up.

[PaulMcClernan]

I did add a refresh button to the revProjectBrowser UI stack (the script closes then reopens it to force-update to the listing) but I like this solution better.

The best thing would be to figure out why it gets out of sync with the stacks / objects in memory in the first place.

If you look at the backscripts library of the IDE, there is a handler that is used to check if revApplicationOverview is open and updates stack's listing whenever a new object is created. It seems to me that there should be an equivelant handler that checks for and updates revProjectBrowser for those same object creation events.