[evlatests] Tuning ranges

[Ken Sowinski]

Rick has been pestering me to know the tuning limits for EVLA
receivers for the transition system.  I determined this empirically
by running a test script in debug mode which covers the expected
range of each band in 100 MHz steps.  For completeness Ka band has
been included even though no reciever is available yet.  All results
are for the direct path of the UX converter.  Use of the conversion
path will extend the range of each band to lower sky frequencies.
Nothing is implied about the performance of the receivers over the
specified ranges.

K   18.0 to 28.0 GHz
A   32.2 to 40.7
Q   38.0 to 50.7