WIP: Constraint generator

[soullivaneuh]

Closes #122

• Constraint class generation
• Test generation
• Move to Twig v2.
• Translation basic generation (for each translation files, even future one. Default key will be used).
• Re-generate translation file for existing constraints (another commit). Check for possible BC breaks.

For translation, try with XliffFileLoader/Dumper.

After that, generate validators for another PR.

[sstok]

FYI:

• You don't have to remove the entire vendor directory just the affected package (and Composer will install the source for only the missing packages 👍 )
• Usually the term "directory" is used rather then "folder" (which is Windows specific).

[soullivaneuh]

@sstok Thanks for your participation! :-)

I think I'll make the command removing the directory itself. 😉

[soullivaneuh]

I think I'll make the command removing the directory itself.

Well, I'll not. It will be safer to have the version from composer.