Updated the function descriptions to be include the new epsrel.
Moved the tril_to_square function to misc_func.py. Also updated it so it
can convert both lower triangular and upper triangular matrices.
Additionally, one can specify the value of "empty" cells. Be default
this is NaN.
Implemented most functions. Error still to be done. Most code very
similar to fisher_harmonics.py
A little more reshuffling (minor)
Updated tri_to_square so that it handles NaN and Inf properly.
Mostly finished Line-of-Sight covariance (have not started with the
error yet)