Refactoring the way sets work internally

Before this can be merged, all providers should be updated to use the
schema.Provider approach.

Next to that a migration path for state files should be added so the
state is converted to use the new internal representation of sets.

And maybe it would be nice to add some eye candy on top of this so
displaying a set on screen (in a plan for example) doesn’t show the
internally used hashes. But that is no requirement for merging this
code.
Refactoring the way sets work internally

Before this can be merged, all providers should be updated to use the
schema.Provider approach.

Next to that a migration path for state files should be added so the
state is converted to use the new internal representation of sets.

And maybe it would be nice to add some eye candy on top of this so
displaying a set on screen (in a plan for example) doesn’t show the
internally used hashes. But that is no requirement for merging this
code.
Merge branch 'f-fix/change-set-logic' of https://github.com/svanharmelen/terraform into f-fix/change-set-logic
Renamed the format function and fix some tests

The new name reflects it’s purpose a little better.
Merge pull request #14 from svanharmelen/f-fix/change-set-logic

Fix/change set logic