[FieldTypes] Split up TaxonomyMultiFieldInfo from TaxonomyFieldInfo and NoteFieldInfo from TextFieldInfo.
- Got rid of Definitions.Values namespace
- Validating in FieldInfo constructor that InternalName doesn't go over 32 char max length
- Removed redundant ToXElement which gets taken care of by Schema property.
- Removed a few settings on IFieldInfo properties to force people to use the non-default constructor (and thus avoid partially initialized FieldInfos)
- Initializing ListInfo collection properties with empty lists to avoid NullRefExceptions