QGAL: Use single arrow in "dumpGraph"
QGAL: Use single arrow in "dumpGraph"

Modify the "dot" format graph to use a single arrow between each
pair of vertices.

Previously we would use two anchors (a black forward one and a
gray backwards). With a single arrow the graph loooks cleaner.

Signed-off-by: Eduardo M. Fleury <54231285b1a7e6820e014049a5428d7993c4be1a@openbossa.org>
Reviewed-by: Caio Marcelo de Oliveira Filho <816df4d2f7553426878b7da6111c247d38d5602a@openbossa.org>

igor-sfdc/qt-wk,igor-sfdc/qt-wk,pruiz/wkhtmltopdf-qt,pruiz/wkhtmltopdf-qt,pruiz/wkhtmltopdf-qt,pruiz/wkhtmltopdf-qt,igor-sfdc/qt-wk,igor-sfdc/qt-wk,pruiz/wkhtmltopdf-qt,igor-sfdc/qt-wk,igor-sfdc/qt-wk,pruiz/wkhtmltopdf-qt,pruiz/wkhtmltopdf-qt,igor-sfdc/qt-wk,pruiz/wkhtmltopdf-qt,pruiz/wkhtmltopdf-qt,igor-sfdc/qt-wk,igor-sfdc/qt-wk,igor-sfdc/qt-wk,igor-sfdc/qt-wk,pruiz/wkhtmltopdf-qt,pruiz/wkhtmltopdf-qt