fix m-type generation for m-types that have the same basename

orogen was so far using the type basename as header filename, which meant
that two types with the same name (but different namespaces) would have
the same m-type filename, for instance:

  base::Wrench
  base::samples::Wrench

would have a m-type generated as base/m_types/Wrench.hpp

This commit switches to the full method name (including namespaces).