[ci] Offloading CI versioning to argotest.

See merge request !8

This commits simplifies the CI setup for this repository, offloading
all complexity to the "argotest" repository.

[fix] Fixes issue #4

Closes #4

See merge request !7

We need to sleep for 1s after killing processes and before we attempt to
remove a container.  However, the sleep was done too early.

[ci] Added argotest-based integration tests

See merge request !6

This commits adds a gitlab-ci integration test target, and the
.integration.nix file, which specifies the exact test version pinning to
use.

Strengthen tests for invalid input

Closes #2

See merge request !5

When creating containers, we would before accept input with empty or
missing cpu or memory lists.  CPU list was also wrongly assumed to be
non-exclusive by default.

Delete fix

Closes #1

See merge request !4

Correctly deal with the case of the last container of the vector being
deleted.

Add a new argument to 'exec'

See merge request !3

We used to pass the environment for the user job implicitly, as the
environment of argo_nodeos_config.  This wasn't very clean and was
causing problems with, e.g., LD_PRELOAD, which gets filtered out because
argo_nodeos_config is suid root.  So now we pass the environment as a
required, explicit argument.

Fix the privilege escalation bug

See merge request !2

Add support for command execution in argo_nodeos_config

See merge request !1

execv doesn't search the path for binaries, making it harder to execute
commands. execvp can be used instead.

Make single-delim-character split() use the string-delims version since
I'm too lazy to fix it separately.

Use standard tools to deal with compile/headers and so on. Autotools are
not necessary easy to use, but everyone knows how to interact with them.

This commit is incomplete:
 - make check doesn't work right now
 - config.h is not used/configured properly

Jsonxx is an import of a third party code, with its own license. While
the licenses are compatible, moving that code to its own directory make
it easier to identify it as foreign.

This commit also remove the extra copy of the code that was in the
repository, and update the relevant Makefile rules.

README moved to markdown, includes project name, description,
instructions, requirements, and links to papers.

Judicael's code, unchanged, extracted from the master branch of pre-ECP
NodeOS repository.

This is not a filter-branch, just a cp -r. We are not losing anything
important in the git history, as it was only 3 commits long, without any
details on the history of the code.