GitLab

Instead of static ordering of simulator types. This simpliefies the
experiment runners but also simplifies adding additional features.
Immeadiate goal is adding network-to-network connections

Preparation to add additional proxy implementations.

Includes an new DistributedExperiment class, a runner for distributed
experiments, a basic sequential runtime, and an example experiment
"dist_netperf" (although scaling beyond 2 hosts is currently still
broken in the rdma proxy).