Added the default arrow shapes to the VisualStyle created during network
import. Updated arrow shape map so that dot's "lvee" and "rvee" map to
Cytoscapes' HALF_TOP and HALF_BOTTOM respectively, and so "odot",
"onormal", and "odiamond" map to the same arrow shapes as "dot",
"normal", and "diamond" since Cytoscape doesn't support open arrowheads.
Added the default arrow shapes to the VisualStyle created during network import. Updated arrow shape map so that dot's "lvee" and "rvee" map to Cytoscapes' HALF_TOP and HALF_BOTTOM respectively, and so "odot", "onormal", and "odiamond" map to the same arrow shapes as "dot", "normal", and "diamond" since Cytoscape doesn't support open arrowheads.