Add position to Location model and acts_as_list
Make sure Location position defaults to 0.
Update Location position on drop.

Current issue: when two Locations end up with the same position, sorting is not
preserved. I must have solved this with Triplocations, so I need to just figure
out how.
Remove Locations render on sync to prevent sorting from skewing order.
Add ordering to a User's positions so they are accurate when server-rendered.
Merge branch 'sortable_locations' into development
Remove fixme comment which no longer applies.
Add debugMode option to rendering Locations to gather more data when problems arise.
Add debugMode option as query parameter to gather more data when problems arise.
Merge branch 'development'