Clean up EdgeInsets to use CF_SWIFT_NAME getter macro

[vicng]

Jazzy won't generate docs for Obj-C headers that use the CF_SWIFT_NAME getter macro (issue filed here).

Once this is fixed in Jazzy, EdgeInsets.swift can be removed and the method signatures in BKYEdgeInsets.h for left and right can be changed back to:

CGFloat BKYEdgeInsetsGetLeft(BKYEdgeInsets edgeInsets)
  CF_SWIFT_NAME(getter:EdgeInsets.left(self:));

CGFloat BKYEdgeInsetsGetRight(BKYEdgeInsets edgeInsets)
  CF_SWIFT_NAME(getter:EdgeInsets.right(self:));