GitLab

`make distclean` now actually removes the external simulators

- change example experiment to pyexps/simple_ping.py
- quickstart.rst: remove repeated information already found in README
- README: add note that simbricks-run is only available in docker containers

- add `Error Opening images/output-base/base.raw`
- move `Getting Help` to the beginning and add content

this gets rid of the non-fatal build error 'No names found, cannot describe anything'

These all do the same thing except with different hosts or NICs. Combine them
in one script running all configurations.
- gem5_i40e_pair
- qemu_i40e_pair
- qemu_e1000_pair

Helps quickly determine available CPU features in host simulators.