- Implementation-level global variable `dirPrefix' of type QString buffers
  the directory prefix of the main .mdl file passed into user level call to
  loadFromMDL(). It is used for finding .cat/.sub controlled units if no
  path is given at their definition.

umbrello/import_rose.{h,cpp}
- At function loadFromMDL() change type of parameter `file' from QIODevice
  to QFile. Reason: Body of loadFromMDL() requires access to fileName().
- New function mdlPath() returns dirPrefix.

umbrello/petaltree2uml.cpp
- At function fetchLocation() add arguments `width' and `height'.
  Reason: Encapsulate scaling by `Rose2Qt' in function body.
- In function handleControlledUnit(), before attempting instantiation of
  QFile(file_name), if file_name is not an absolute path then prefix
  Import_Rose::mdlPath() to it.
- In function petalTree2Uml(),
  - Store original parentPkg in parentPkg_sav;
  - Before for-loop calling umbrellify(), if parentPkg is NULL then set
    parentPkg to umldoc->rootFolder(Uml::ModelType::Logical);
  - At shortcut "return true" after for-loop, test parentPkg_sav in lieu of
    parentPkg.