Squid: Avoid cycle between java packages

https://trello.com/c/A0rrIWb0

Resolved packages dependency cycle in MOTECH CommCare API
* Moved CommCareAPIHttpClient to client
* Moved appropriate tests to fit the new packages order

Change-Id: I8a5c88e2d9c1ee3008dc7d39a86573bef3799151
Merge "Squid: Avoid cycle between java packages"