[evlatests] setting reference antennas

[Ken Sowinski]

On Tue, 22 Jul 2008, Ken Sowinski wrote:

> I have placed a script 'setrefant' in /home/mchost/evla/bin which
> uses the long-ago-implemented REST interface to the PhysicalAntenna
> to set a reference antenna or antennas.  The choice remains in place
> for the duration of the scrupt currently executing.  If a new script
> is started another reference antenna choice will need to be made.

This does not work.  It does indeed set the PhysicalAntenna property
as desired, but that is irrelevant to the operation of the array.
It turns out that the marking and honoring of reference antennas is
entirely an agreement between the .evla script and idcaf and is
communicated by intents.  Any observation-time effects of reference
antennas is mediated in included .py files used by the script.

This makes it impossible to alter the reference antenna choice without
modifiying and restarting the script.  We should decide whether this
is really the behavior we want.