Updated TODO list
Moved DataErrorInfoTrait to Masamune.Obsolete assembly
Merged changes from the branch 'dev_v22'
Updated TODO list
Marked DataErrorInfoTrait obsolete
Added a new stuct DataErrorInfoMixin, a clone of DataErrorInfoTrait (the name ot the struct was logically incorrect, it's a mixin, not a trait)
Merged changes from the branch 'dev_v21'
Updated TODO list