Help site deployment

With the `ome-help` repository being ready to go into production, this PR updates the `gh-pages` branch to merge the latest changes.

/cc @gusferguson @hflynn 

NB: merging this PR will still update http://openmicroscopy.github.io/ome-help/. A follow-up PR will be opened to deploy help at http://help.openmicroscopy.org.