I had conflated the data structure I wanted to use for sending a
request to the service vs. having the service be able to respond.
This is the first step to separating out the two.

This is a vestige of when I did a wpkg sync in OnStart, which
thus needed not to block. Now, the wpkg commands only run
in response to a WCF message rather than via a standard service
control method - and I want them to block until, for the purposes
of returning info to the tray notifier app.

Our wpkg sync script impliticly assumes we're running 64bit because it
reads from (implicitly by default) the 64bit view of HKLM\software.

We only support 64bit machines so building only for 64 bit seems like
the easiest solution. Figuring out what to change if we ever need to
support 32bit Windows 10 is left as an exercise for the reader!

By default, an eventsource of WpkgInstaller gets created in the
Application log. We have to use a different eventsource name.