WIX installer: add checkbox options for PATH editing and other actions

Split from #1620

The old NSIS installer had these options:

By default Dr. Memory does not adds its directory to the system PATH.
() Do not add Dr. Memory to the system PATH
() Add Dr. Memory to the system PATH for all users
() Add Dr. Memory to the system PATH for current user

[] Create Dr. Memory Desktop Icon

It's non-trivial to duplicate that in the WIX installer.

We may also want a checkbox for launching the README.