Default files (1)

First PR for the defaulted files and parsing method.  Here's the layout:

- ```share/antioch_default_files/``` contains the default files
- ```configure.ac``` defines the default values of the file path _ANTIOCH_DEFAULT_FILES_PATH_ and the file names.  The files' path is initialized to the ```share``` folder of the source files, ```make check``` uses this value.
- ```Makefile.am``` makes use of the _install-data-hook_ to change the value of the default path to the installed share directory.
- full backward compatibility is ensured by playing with default values in the ```ChemicalMixture``` constructor.
- some cleaning too, the typename ```Species``` is conserved for clarity, it's ```typedef```'ed to ```unsigned int```, the unnecessary maps have been deleled (```active_species_name_map``` and ```species_list_map```).

As for errors and warnings, only the chemical species information needed at construction time are mandatory (name, molar mass, formation enthalpie @ 0 K, rotational-translational degrees of freedom and charge), vibrational and electronic data are optional, if not present, only a warning is issued.

Thermodynamics and transport defaulted data to be in others PR, to make it easier to review.