MF.getInfo should always return the same type

[lpatiny]

Changing the property name in the return value is an issue and we should remove this feature

Related to:

• MF info properties untyped #226
• mf-parser: MF.prototype.getInfo can be incoherent on successive calls due to caching #232
• refactor(mf-factor): getInfo is complicate with parametrized dynamic properties #259