Add sorting by optimum path to the Zone Completion Assistant

[SamHurne]

It would be neat to be able to sort objectives in the Zone Completion Assistant by an optimized zone-completion order.

See http://www.ownedcore.com/forums/mmo/guild-wars-2/402066-guide-exploring-world-optimized-way-all-areas.html for a guide provided a basis of the order of zone-completion.

[CJICantLie]

I was figuring we would see people posting tasks .xml files with essentially this very thing on the forums.