[WiP] Add startup script with worker core support

[ivan4th]

trafficstars

Non-empty value of VPP_USE_WORKER_CORE env var enables the use of the worker core. In this case, exactly 2 logical cores must be allocated for the VPP container via the cpuset cgroup controller.

• [x] initial version of the script
• [ ] verify that it's working for "classic" (workers 0) case
• [ ] verify that it's working for "multicore" test
• [ ] merge #83 and update this PR to remove extra commit
• [ ] remove -x from #!/bin/bash in the start.sh