[meta] Split the core, next

[Hywan]

After #96, we must continue to split the core. Goal: Remove Hoa\Core.
We have to split Hoa\Core\Parameter and Hoa\Core\Data, and also Hoa\Core\Core. What is the strategy here? We must (i) find namings and (ii) find if they must exist (if they have a future). What do you think?

[Hywan]

• Hoa\Core\Data can be moved to Hoa\Xyl, the only place where we use it.
• Hoa\Core\Core can be removed totally.
• Hoa\Core\Parameter needs a better name. Any idea @hoaproject/hoackers?

[Pierozi]

Hoa\Core\Parameter to Hoa\Core\Config or Hoa\Core\Constant because roughly its value will not be changed after it's defined.

[Jir4]

i disagree, Hoa\Core\Parameter didn't just set constant. There's an interface used in several other rep.

[Hywan]

Back to #96 for a more comprehensive list of tasks.