Documentation, argument order, and demo changes in vnf_tri_array

[amatulic]

• Re-ordered args in vnf_tri_array() for consistency with vnf_vertex_array()
• Using same arg handing logic as in vnf_vertex_array()
• Edited arg documentation in vnf_tri_array() for consistency with vnf_vertex_array
• Modified wrapping and capping demos to use equal-length arcs, removed them from vnf_tri_array(), moved them into vnf_vertex_array()
• Changed viewport distance for cymbal example, made image medium size