Configurable enum

[yann-eugone]

see #24

• Add the 2 configurable enum classes to the source code
• Add testing for those two classes
• Add more documentation about usage and examples
• Add enum autoconfiguration within the bundle extension

[yann-eugone]

@J-Ben87 what do you think ?

• https://github.com/yokai-php/enum-bundle/blob/configurable-enum/README.md
• https://github.com/yokai-php/enum-bundle/blob/configurable-enum/Resources/doc/declaring-enum.md

[J-Ben87]

I like it! You allowed the different solution in a non intrusive way, I can't think of a better solution.

[yann-eugone]

What about the documentation ? Do you think it is clear enough ?

[J-Ben87]

I think so. Maybe because I already know how to use it, but it seems pretty clear. You detailed all the ways to declare enums, how to integrate it with Sonata...
Maybe you could add a little note on how to use it in forms without type guessing, or on how to use the translated enum.

[yann-eugone]

Just added more documentation, and fixed some important inconsistent issues with namespaces (from symfony 3 to symfony 4 conventions)