yang.common.QName is a YANG identifier

This has cropped up from MDSAL-309 and MDSAL-300, when Binding V1 is creating Java identifiers from QName.localName(). Due to historic reasons coming from SchemaNode design, localName() is quite permissive in what it accepts and hence MD-SAL considers a lot of crud, line spaces in BindingMapping.getClassName() – which is fed solely through YANG Identifiers.

Clarifying a YANG Identifier localName() contract, it's relationship to XML localNames used by XML parser would be useful – especially in the are of anyxml/anydata content.