Support enhancements to Cisco CSR VPN REST APIs

Incorporate latest enhancements and fixes in Cisco CSR router REST API
to the VPNaaS device driver and unit test cases. Primarily, is support in
the REST API for different IKE and IPSec encryption algorithms, name length
error handling, disable of anti replay window, and IKE keep alive.

Also includes minor typos and comment fixes mentioned in previous reviews.

Change-Id: I931f487fbd4ead93a1648e89c9c383b3d55fc07c
Closes-Bug: 1303820