Allows parameters to be set from saved XML and changes the
parameterEditor buttons (currently for discrete parameters only) to
reflect which parameters are currently used by selected and
non-selected channels. This fixes a problem where the buttons would
always show what the last press was rather than the current values for
the active channels (e.g. If you changed the parameters on Channel 2,
and then switched to select only Channel 1, the GUI would incorrectly
indicate that the settings for Channel 2 were active). Additionally,
allows the user to see what parameter values are used for channels not
currently selected.

The ReferenceNode (digital reference) is now working, although its
functionality is limited. Currently, only one channel can serve
as a reference. Ideally, each channel or subset of channels could
have a unique reference. This will require additional UI upgrades
that are not a priority at the moment.

Some caveats:
- If a source doesn't generate its own timestamps, all timestamps will be
  zero. This is obviously bad, so we need a way to protect this
  from happening.
- If there are multiple timestamps from different sources, they might
  conflict. Again, something needs to be done about this in the near future.
- If only a 32-bit timestamp is given, it needs to be shifted by 8 bits
  to fit in our 64-bit timestamp slot