TypeUsage -> TypeDefinition+TypeUsage

[KitsuneRal]

Translator::mapType() now has to make a copy of TypeUsage (with all its attributes), which is very inefficient given how many times types should be resolved while analysing API specs. The situation can be solved easily for non-parameterised types by pointing to the type instead of copying. For parameterised types it's more complicated since that pointer would need to be accompanied with type parameters. As noted in the comment in Translator::mapType(), TypeUsage should become a "smart handle" to an instance of a newly-made TypeDefinition structure that would own all the stuff TypeUsage now has, except innerTypes.