[WIP] Full VCS modelling

[e-koch]

Adding the full VCS models based on the underlying theory. The model is described in Chepurnov et al. 2015, Chepurnov et al. 2010, and Chepurnov & Lazarian 2006.

Remaining issues:

• Chepurnov+2015 describe a normalization procedure for the emissivity component, which includes a normalized form of the fourier transform of the window functions. Only the normalization part for the emissivity spectrum is implemented and this can overestimate the window functions.
• Limits on the volume integral need to be checked.
• The model requires numerically integrating many times for each data point... and this makes things rather slow. The underlying functions are implemented in cython and this gets the evaluation down to ~1/2 sec. per data point.
• The volume integral can be very slow to do in quadrature. Monte Carlo integration is used instead from the vegas. The package will be added to the list of optional dependencies.

[e-koch]

Testing out the arb library for a faster general hypergeometric function. Here's install instructions so I don't forget:

git clone git@github.com/wbhart/flint2.git
git clone git@github.com:fredrik-johansson/arb.git
git clone git@github.com:fredrik-johansson/python-flint.git

cd flint
./configure
make -j 4
make install
cp libflint.* ~/anaconda2/lib

cd ../
cd arb
./configure
make -j 4
make install
cp libarb.* ~/anaconda2/lib

cd ..
cd python-flint
python setup.py build_ext --include-dirs=/path_to/flint2/://path_to/arb/

I think I installed gmp with apt too.

If it worked, import flint should work in a python terminal.