Triangle and Diamond Marker clean-ups

Hi Inkscapers!
  first of all many thanks for sharing and developing Inkscape! It's one of
my favorite pieces of free software.

The attached patch adds several triangle and diamond markers that are
placed properly to be used with the connector tool. The problem was that
the triangle and diamond overlapped with the objects they were connected
too.

The fix was achieved by adding a translate in the transform.

Additionally sets of markers were added that are unfilled triangles and
diamonds, which are useful for creating UML diagrams.

This was achieved by adding a "fill:#FFFFFF;" to the style attribute.

See

http://en.wikipedia.org/wiki/Image:KP-UML-Aggregation-20060420.svg

and

http://en.wikipedia.org/wiki/Image:KP-UML-Generalization-20060325.svg

for uses of these markers.

Let me know if there are any problems.

Best regards,
  Christopher