Sync applications against clickops-created dev teams

Closes gateway-ops#103

See merge request !3

Sync Apigee X apps and developers

See merge request !2

Run a plan before apply-ing it so that the changes made are auditable.

It would appear that the terraform provider does not deal well with
attributes with empty values so, for the moment, skip any attributes
which have empty values.

Suggestions for improvements to terraform sync job.

See merge request !1

Adds the ability to sync attributes for apps, credentials and developers,
Encourages the user to keep all data gitignored,