3.0 rc

[shmax]

Rewrite library with a new approach:

• Divided old UserErrorsType class into a an abstract ErrorType base and subclasses for each of the types (ie. 'StringErrorType, InputObjectErrorType`, etc
• Moved the validation work that was formerly happening in ValidatedFieldDefinition to the ErrorType family of classes
• For listOf type, you can now do separate validation for the list of items as a whole, as well as each individual item in the list
• there is no longer any concept of subErrors for input object types; to mitigate the possibility of field name conflicts, code and msg have been renamed to __code and __msg. Same goes for most of the other generated fields ('__valid', __result, __path)
• Created own namespace for everything instead of piggy-backing on existing ones