[evlatests] parameter simplification for the VHF receivers

[Ken Sowinski]

Currently parmainator distinguishes between 75 MHz and 300 MHz for
band related paramters.  The parameters of interest are subreflector
rotation and focus and band-dependent delays.  Also there are T_cals,
which are now obsolete in the paramters DB, and tables of attenuator
settings, also obsolete.

I suggest that we have only one band code "VHF" to select the low
frequency receivers.  Receiver.java will transform any reference
to "75MHz" or "300MHz" to "VHF".  This allows us to keep only
one set of parameters in the DB, rather than two identical sets;
prevents possible mistakes when two sets are maintains; more
accurately reflects the current hardware; and, eliminates the confusing
necessity of having to know whether the script selected "75MHz" or
"300MHz".

The rational is that there is one receiver box containing all
receivers.  Its single output (dual polarization) is conneted
to one T301 input.  Regardless of which band is selected, the
hardware configuration is the same and the same wideband signal
is presented to the T304.

Would doing this prevent anything that would be practical and useful
with the current scheme?