Add dictionary type

[nsensfel]

A dictionary could be added without any modification to Wyrd by using lists of (cons KEY_TYPE VALUE_TYPE).
KEY TYPE would have to be a comparable type (same as with a set).

[nsensfel]

This conflicts with structure declaration in Fate, as those as referred to as dictionaries. Putting this as a V1 milestone to avoid having to break backward compatibility right away.

[nsensfel]

dict_to_list, dict_from_list, dict_keys, dict_values, dict_merge, dict_filter, dict_set, dict_remove , dict_has, and dict_get.

[nsensfel]

Enough has been done to ensure that backward compatibility will not be broken. Actual implementation of this feature is not urgent and can wait for the milestone following a stable release.