Add a dummy connector to facilitate testing of caliper (also useful for build automation)

[davidkel]

Caliper has many capabilities and unit tests aren't going to cover testing these capabilities. For example testing the behaviour of different rate controllers. If we add a dummy connector into caliper this affords us a lot of options as well as not having to have a real blockchain environment to test out caliper capabilities. We could then have integration/end to end tests that use this dummy connector to test the various aspects of caliper-cli and caliper-core as well as reduce the builld times when not testing connectors specifically.

this dummy connector could also be configured to vary it's response times either deterministically or randomly.