Remove unmaintained and crippled "offline tool"

198da6f accidentally removed the ability for the "Offline" tool to be
used off of search results -- thus removing its ability to be used for
offline ticket editing, and limiting it to only offline ticket creation.
As it has a number of other notable bugs and limitations, prune it
entirely.
Add a note about the offline tool removal
Merge branch '4.2/remove-offline-tool'

Conflicts:
	docs/UPGRADING-4.2