DataFrameSchema.equals() including order and CompareResult.Matches

[Jolanrensen]

Fixes #1502

and fixes the fact that
dataFrameOf(a, b, c) != dataFrameOf(a, c, b)
but this used to be
dataFrameOf(a, b, c).schema() == dataFrameOf(a, c, b).schema()

• Replaced usages in the library of DataSchema.equals() with .compare() (This will also carefully need to be checked in the compiler plugin, though I think .compare() is already used there, which is good!)
• Changed behavior of DataSchema.equals() to only return true if the order matches as well
  • (That allows us to write proper move {} tests in the compiler plugin! Because we can now check compileTimeSchema() == runTimeSchema() and the order is checked too)
• To avoid confusion with the name, I deprecated CompareResult.Equals with Matches. Usages in the library are updated, but this will also need to be updated in the compiler plugin.
  • (This opens the future opportunity to reintroduce CompareResult.Equals as "equals exactly with order")