Import and use fahinstall's download() function.
Use smarter approach to trap premature exit.
Revise Mono package list.

We need to add libmono-system-data-datasetextensions4.0-cil as it's
dynamically loaded by System.Data.SQLite (implicit dependency).

Drop mono-runtime and libmono-system-core4.0-cil as they already
are pre-requisities for other packages we're installing.
Ensure that desktop shortcut is owned by appropriate user.
Switch to team33-provided HFM build.
Also rework installation process to accommodate top level directory
that is now included in the archive.