[ci] Fixes the pipeline stage order: readthedocs for "latest" should be last.

See merge request !96

Resolve "readthedocs"

Closes #47

See merge request !80

This commits also moves the manifest schema to a yaml-rst literate file.
The documentations covers nrmd/nrm, the manifest schema, and libnrm.
The commits also renames containers to slices and adds example
manifests, which are now used in CI directly from the nrm source.

[feature] Move the manifest file format from JSON to YAML.

See merge request !93

Resolve "Support adding bind mounts to container for runtimes that allow it"

Closes #52

See merge request !92

[ci] moves CI back to `master` after a coordinated libnrm+nrm update.

See merge request !91

Use json schemas for message formats

See merge request !90

Adds the nrm/schemas repository which defines the communication schemas
for the upstream and downstream APIs. The messaging.py file now uses
decorators and two added python dependencies (jsonschema and warlock).
This commits also adds the .envrc direnv configuration file for
nix-based development.

[doc] add working manifest for singularity

See merge request !89

Document what we want in the manifest for singularity support.

Container singularity support

Closes #42 and #49

See merge request !85

Instances in singularity are basically the same as being able to create
an empty container and then run something in it, so we can have the same
thing as with nodeos.

One main issue with the code as is: we should probably refactor the
container_manager code to modify the manifest on the fly according to
the options listed in it. It would make it easy to pass along stuff like
PWD, necessary binds and so on.

Self-explanatory.

If monitoring is active, make sure to export the
ARGO_NRM_DOWNSTREAM_EVENT_URI variable required by libnrm.

Fix #49.

The daemon can be configured to launch singularity containers. In such
case, the manifest must contain an image section.

Note that this doesn't support any resource management with singularity,
since that stuff is only available as root. We will add a second
container runtime option to support it later.

Resolve "Uncaught execption in daemon when argo_nodeos_config not available"

Closes #39

See merge request !86

This catches the exception and sends a message on the log with
the ERROR level.

Resolve "cmd does not forward CWD"

Closes #40

See merge request !88

Make the container Popen pass the working directory from the `nrm
run` call, through the $PWD environment variable.

[fix] update zmq and tornado to latest available

Closes #31

See merge request !60

Fixes #31: refactor the code so that the ioloop is not install
forcefully, as zmq and tornado can work better now.

Resolve "Names of the NRM binaries"

Closes #41

See merge request !83

Resolve "Names of the NRM binaries"

Closes #41

See merge request !81

cmd -> nrm
daemon -> nrmd
argo-perf-wrapper -> nrm-perfwrapper

This converts the return status to int before running the
introspection logic and fixes the issue.

Resolve "`cmd run` error code"

Closes #44

See merge request !77

[typo] Fixes typo.

See merge request !76

Resolve "`cmd` stdout flushing"

Closes #45

See merge request !78

This gives automation tools an easier time when streaming data from it.

Resolve "`cmd run` SIGTERM handling"

Closes #46

See merge request !79