Adding Quickmodel script the option to use informed F_PL priors

[MehtapIsik]

We would like to be able to provide an informed F_PL prior based on previous experiments for Quickmodel analysis. Currently, it isn't possible to modify F_PL prior in Quickmodel analysis. We should make F_PL an accessible parameter that we can modify through input.py file for Quickmodel analysis.

[MehtapIsik]

F_PL from an previous experiments Quickmodel run results can be extracted from the pickle files.
We should create a separate utility script for extracting F_PL from pickle files and place it under assaytools/scripts/ directory. Since pickle files are very large and difficult to store it would be more flexible to have this as a separate script.

Example script:

import cPickle
data_file = 'Src-Bosutinib-AB_mcmc-2017-06-18 08:42.pickle'
with open(r'%s'%data_file,'rb') as my_file:
     data = cPickle.load(my_file)
F_PL_mean = data['F_PL'].mean()

However, that this script above takes the mean from the entire trace, not just the equillibrated trace. We think that equilibration time (t_equil) should be extracted from json file, which was determined based on equilibriation of DeltaG value. We should throw away the same amount of equilibration time from the trace of fluorescence and calculate the mean F_PL.