Graph#rebase
work towards using prototypes for entities
Working more-efficient parentWays
Working rebase
working parentRels
Fix difference
Merge takes an entities object, not graph
Don't re-add removed parentways, don't duplicate
Change the midpoint data a bit

Store the ways which share the segment and the index of
the segment. This will be used in both DragWay and Draw
behaviors.
Extract AddMidpoint action
fix inspect icon on warnings.
Merge branch 'master' of github.com:systemed/iD
Small parentWays, parentRelations perf improvements
More draw refactoring
Fix drawing on midpoints (fixes #559)
Rearrange code
midpoint = true -> type = 'midpoint'

Makes it more consistent with entities.
Add tests for #replace #remove #rebase
Merge remote-tracking branch 'systemed/master' into graph-perf2
Fix graph.rebase()