Rx antenna pattern

[Doreban]

Added functionality to borealis to accept a function defined in the experiment that will return specific phases for the rx antennas when processing data to rawacf.

[Doreban]

See experiment pull request: SuperDARNCanada/borealis_experiments#10

[RemingtonRohel]

This looks great, there are a few more things that should be done though:

• Update the docs
• Create some failing tests of bad rx_antenna_phases that fail experiment_unittests.py to ensure that the validator is well-behaved

[Doreban]

Updated the docs where I could determine that rx_antenna_pattern should be talked about.

Also added 5 new tests to fail the unit test when testing rx_antenna_pattern:

• not callable -> fails if the passed parameter is not a function
• magnitude -> fails if any element of the result is greater than 1
• wrong shape -> fails if the dimensions of the output array are not [beam_pattern, num_antennas]
• not ndarray -> fails if the return value is not an ndarray
• bad intr return -> fails due to improper shape of return. The rx_antenna_pattern returns a correct result for the main array, but an incorrect shape when run for the interference array (assumed an offset parameter of -100 and type float)

all five tests were run on sdc-lab and they failed with the expected returns.

The new full_fov.py experiment (using the rx_antenna_pattern option) also passes the unit test still.

[RemingtonRohel]

Small typos in the docs, but otherwise looks good!