Fixes #1929, update toolbar examples in activity doc strings

I went all out with a big example, but I think since that is what most activities use it is a good idea :smile:.

> I think we really should try and document the stuff well, It can be helpful. Maybe we could even put all of the doc strings on developer.sugarlabs.org? We seem to have good doc string coverage so we may as well keep this up to date and use this great resource :smile_cat: