Restore original name of test_plot.py

I plan to move this script into the Python package as
lalinference.test.test_plot. So the all-lowercase name makes more sense
than the CamelCase name.
Skip image comparison tests if scipy < 0.8

We need the method scipy.stats.beta.interval(), which was added in
Scipy 0.8.
Enable LALInference python unit tests
Use I0(snr^2 |autocorrelation|) for timing likelihood
Factor out signal model
Whitespace
Faster, and less alias-y, method of computing autocorrelation
Implement new autocorrelation likelihood in Gaussian quadrature functions
Track API change in LALSimulation
Suppress underflow errors
Whitespace
Make sure maxpix is set even if resolution is given explicitly
Oops, incorrect treatment of log_offset
Use C99-style loop variable declaration
Parallelize TOA loop
Use Gauss-Legendre quadrature over cos(inclination)
WIP: report number of function evaluations
Revert "WIP: report number of function evaluations"

This reverts commit 8310e39bb938a47eb2ee1dd4f40fdb7d07e9bc66.
Use fixed-order Gaussian quadrature for distance in toa_phoa_snr
Add macros for branch prediction hints