Rename (and correct a bug into) the SFH quenching module to sfh_quenching_trunk
and add a sfh_quenching_smooth version where the SFR is linearly decreasing
after the quenching.

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.

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

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

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.

Normalise the SFH appropriately in the same if then else statement. Bonus is that is saves an array multiplication if a specific scaling factor is not given.

When computing the galaxy mass, convert from yr to Myr outside of the integral. That way we only multiply a scalar by 1e6 rather than a large array. Good for speed and memory bandwidth.

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.

Addition of a new module performing a quench on the star formation
history.  We must change a little the SED object to allow the
modification of the SED.