Update debugtoolbar.rst

Fix wording to reflect how debugtoolbar actually works
Update debugtoolbar.rst

grammar fix
Merge pull request #1298 from tylereaves/master

Fix wording in debug toolbar tutorial
minor tweaks based on toolbar changes in 2.x
More explicit example of set_property

cleanup callback has a "request" parameter (and not "_")
cleanup callback know (since 1.5) if an exception occurred or not (to commit or rollback)
(same as #1302 on 1.5)
Merge pull request #1303 from flibustenet/patch-2

More explicit example of set_property