We do not store the time grid in the SED anymore given that we assume it starts at 0 Myr with steps of 1 Myr, we can easily reconstruct to save it if needed. It should save a little bit of memory and it should go a little bit faster.

The name creation_modules is a bit vague. For more clarity and consistency we rather use sed_modules now

Specify the types and the constraints of the input parameters for the SED creation modules and the analysis modules. Once validation is activated, the validation module will be able to infer the constraints from the specified information.

Modules were a bit inconsistent how the input parameters are used. It was not always ensured they were the right type, they were sometimes read several times, and finally they were not always obtained from the _init_code() method. This is an attempt to clean that up as much as possible.

Simplify the construction of modules by remove the out_parameter_list dictionary. It was not used anywhere, was not always provided, and was not even up to date.

Switch back to ordered dictionaries for the input parameters after all. That way the list of parameters is kept into a logical order when building the configuration file. The impact on performance is negligible.

We rely on OrderedDict to keep the order of the parameters. However given the way the code is structured currently, there is really no reason for this. So let's just switch to the standard dictionary. This has two advantages. First the standard dictionary is much faster than OrderedDict (implemented in C rather than in pure python). Then, standard dictionaries are marshalable, which makes them usable as keys for other dictionaries.

Update CIGALE to clean anything related to 'average_sfr' and replace it by 'sfr10Myrs' and 'sfr100Myrs'

The "galaxy_mass" parameter must not be set to 1.0 in the stellar
emission modules because when using CIGALE to generate SED without
normalising the 1.0 is wrong and misleading.

Instead, we compute the real galaxy mass (the integration of the SFH) in
the star formation history modules.

Change how the IMF is handled. Now rather than a string with require an integer. It is slightly less user friendly but it will make possible to store all the sed.info in a numpy array, which reduces the amount of memory required per model.

Treat the total galaxy mass as a normal parameter. The special handling of galaxy_mass already got removed in the previous commit.

Remove the possibility to use the same module several times. Simplification of the code ensues. Now sed.info keys are prefixed with the characteristic of the module (stellar, nebular, etc.).

Extend the Calzetti-Leitherer with the Leitherer formula below 91.2 nm.
Maybe we should made the attenuation even stronger there.

Stop cutting the Maraston 2005 SSP below 91.2 nm.

Remove the author email addresses from the source files and add a AUTHORS.rst
file with the addresses and current affiliation to make it easier to update
the information.

Also, give copyright to the University of Cambridge and the University of
Crete for code developed by authors working there.

It will make the documentation clearer.

For the creation and analysis modules, move the contents of the
common.py files to the __init__.py.

Move the SED creation modules to pcigale.creation_modules to be more
consistent with the analysis module location.

Instead of prefixing the key in the SED with the module name, we postfix
them with the same postfix as the module name if any. This makes easier
to inter-change modules adding the same information (for instance
attenuation modules adding the attenuation value).
That implies that when using several modules adding the same
information, one must postfix the name of each.

So that the configuration files and the serialized data have a logical
order.