MOTECH-620: Migrate Schedule Tracking to MDS

This commit moves the persistence source from CouchDB
to Motech Data Services for the Schedule tracking module.
Some refactoring was necessary to make it possible.

Change-Id: If7957d1f098a25c4d951be4ba12fd20d7046750d
Twilio SMS Provider change

Change-Id: Ibbe2284a615c742bae84ae7f022e692f0973b7bd
Allow using headers and authentication in the Http Agent

This commit adds the same support for the headers and authentication
as the change on 0.21 branch, plus adds the same ability for
the HttpAgent.

Change-Id: I12854f4f8a855bb8c261831fb5b201e7e4942f7a
Merge "Twilio SMS Provider change"
Clean up modules after config migration

This fixes the build by removing leftover ektorp
dependencies.

Change-Id: Iea33ca8f65e1ad7fbedbee9b05d5ac82f0b585d4
Merge remote-tracking branch 'origin/master' into dev/mtraining2mds