Replace (almost) all parsable enums to an enum-like class

[Rapougnac]

Description

Connected issues & other potential problems

Closes #661

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (it's a partial breaking change?)

Checklist:

• Ran dart analyze or make analyze and fixed all issues
• Ran dart format --set-exit-if-changed -l 160 ./lib or make format and fixed all issues
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works

[abitofevrything]

Could you also deprecate all the parse constructors? They will probably be removed eventually considering that they're now just duplicate functionality.