feature linkout to URL based on template is broken

[GreggHelt2]

Used to be a right-click pulldown option to go to URL for more info on feature (for non-annotation feature tracks). During merge with JBrowse 1.7, right click menu got changed, need to add URL link option back in.

[rbuels]

See http://gmod.org/wiki/JBrowse_Configuration_Guide#Left-click_Behavior and the Right-click behavior below it.