CIMI: map cimi networks and forwarding groups to Deltacloud
subnets and networks
CIMI: expose import and export of systems and system templates
for drivers that support these operations
CIMI client: fix typo fcgp->fgcp
CIMI Systems: fixed id not being set for SystemSystemCollection.
This was missed in the patch for DTACLOUD-559
(commit 640405627827bdf0d38e3418647d2d36fd272d74)
Also, applied name change of add_/remove_ methods to collections.

    https://issues.apache.org/jira/browse/DTACLOUD-559
    https://github.com/deltacloud/deltacloud-core/pull/28
    https://github.com/deltacloud/deltacloud-core/pull/27
Client: Lock the 'minitest' gem version to '<5.0' because of bug in turn.
Fix failing travis builds - also DTACLOUD-562

https://travis-ci.org/deltacloud/deltacloud-core/builds/7731674
https://travis-ci.org/deltacloud/deltacloud-core/jobs/7763133
https://issues.apache.org/jira/browse/DTACLOUD-562
Tests: added assertion to mock image test for 'CreateImageNotSupported'