Simplify and streamline the production of mock plots. Now just output one plot per file and do so in parallel. Also output in log when it seems to make sense.

When the flux file contains a mix of spaces and tabulations as column separators, pcigale discards the header and takes the first data line as the header. Now pcigale properly handles such a combination. Bug reported by Paola Santini.

Actually raise an exception indicating to the users to change their
parameters if the quenching age happens to be superior to the galaxy
age.

Fixes #2

A dummy parameter was used in param because a parameterless module is
not possible.  Now that we have the list of filters, we can remove it.

Using the param module, if the list of filters is empty, no flux will be
computed and the module won't complain about '' missing filter.  Also,
switch the default value for this list of filters to the empty string,
because None means that there is no default value which makes the module
not usable without the list for filters parameters.

Closes #5

The luminosity table is also used when plotting Fluxes to access the
various components.

Ensure that the Lyman continuum emission is properly absorbed by the gas in the nebular module. This means that without that module, the Lyman continuum is left untouched. As this may be an issue for people used to running without the nebular module (assuming that the flux in individual bands in small), add an option to only absorb the Lyman continuum while discarding any nebular emission.

Implement a simple verification of the list of modules to warn the user if some mandatory modules are missing.

Remove the radio component from the dale2014 model so that it can be used with the more flexible radio module, courtesy Daniel Dale

Handle the case where we do not know the redshift to estimate the physical parameters by taking all models at all redshifts. This means that in effect pcigale can also act as a photo-z code now on.

Now that we leave the models with NaN fluxes, the scaling factors and χ² may be NaN too. Handle this case.

The galaxy_mass parameter confuses a lot of people. Change its name to sfh.integrated because it is actually the integral of the SFR.

Add an _init_code() to sfh2exp to avoid repeating twice the same operations. Even though that should not be a common occurrence, it is cleaner by separating the computation of the data and the actual processing of the SED object.

The SSPs in the database are always built on a time grid with 1 Myr time steps. No need to drag around a constant for this as it will stay that way for the forseeable future.

By construction the SFH in cigale is a comb. Every 1 Myr stars are formed. All at the same time. In effect star formation is not continuous. This means that we should not use trapz to integrate the SFR or use an analytic relation. Rather we just sum, which is correct for the discrete nature of the SFH.

Rename the SED info dictionary key for the AGN faction added by dale2014
module from agn.fracAGN to agn.fracAGN_dale2014 to avoid conflict with
fritz2006 module.

Avoid multiply the array by a scalar once rather than twice. It makes the computation quite a bit faster.