User visible changes: Add man page for rmtoo invocation.  Add
additional check: there can be only one master requirement.  In LaTeX
output both dependency directions are now available (Fixed Bug
2958650).  The Emacs req-mode.el is now included in the tar ball.
Priority of requirements is now included in the graph.  Better error
handling during requirement dependency handling.  Usable priority
computation now ready: based on parents and own weight (Fixes Bug
2959733 and 2959560).  Add a lot more requirments for rmtoo itself.
'Note' is now highlighed in Emacs req-mode (Fixes Bug 2951708).  Check
for strong connection components (directed circles) added (Fixes Bug
2958645). 

Internal changes: The graph and the anti-graph are now build.  Add
possibility to specify dependencies between modules (Fixes Bug
2960010).  Add a digraph library - which is needed for detecting
directed circles (Fixes Bug 2960008).  Add toplogical sort into new
digraph library.  Fixed problem of integration of digraph library into
the RequirementSet class.

