QP/C 5.4.1 released

The QP/C 5.4.1 release changes the active object class hierarchy so that QMActive is now more fundamental and is the base class for QActive. (Previously QMActive was a subclass of QActive). The newly added documentation section about QP/C Design shows the current class hierarchy.

NOTE: Because the types QMActive and QActive are equivalent in QP/C,
this change has minimal impact on the applications, but it is now more
correct to use QMActive as the base class for all "opaque" active object
pointers.

Also, this release brings several cosmetic improvements:

1. All QM models included in examples have been modified to use the
   QMActive "opaque" pointers.

2. The ROM-able QP version string QP_versionStr[] has been added and
   used consistently in the macros QEP_getVersion(), QF_getVersion(),
   QK_getVersion(), QV_getVersion(), and QS_getVersion() macros.

3. All Makefiles for the GNU toolset have been cleaned up, whereas any \ (back-slash) characters in the paths have been repalced with /
   (forward-slash) characters.

4. Several README files have been updated.