Change jstestnode arguments to accept the [desired capabilities](https://github.com/SeleniumHQ/selenium/wiki/DesiredCapabilities) as a JSON object, so that we can run jstestnode tests on any selenium server ( the target being nexedi/slapos!420 ), not only saucelabs.

This MR also introduces some JSON schema for instance parameter.

/reviewed-on nexedi/slapos!429

https://www.theia-ide.org/

/reviewed-on nexedi/slapos!417

@tomo @rafael if you have any review on this (should be ok as its kind of same commit than last update one, but well)

/reviewed-on nexedi/slapos!433

Improves 57bdf689 by having stored and
expected values stable across runs.

Also assertion is done with {hash} instead its real value, as it has no
meaning to test user.

this is a followup of nexedi/slapos!427

/reviewed-on nexedi/slapos!431

Cloud & Desktop IDE https://www.theia-ide.org/

This version is inspired from "theia-full-docker" from
https://github.com/theia-ide/theia-apps so it includes all extensions.
Many language servers are missing in this version (basically only go,
typescript and python language servers are installed).
PHP extension is not even installed.

Previously it was required to put \ into multi-entry gowork.install,
because the way it was processed was to directly pass it into bash
command, and if \n were there the command was cut by bash and the
trailing was considered as another command.

We can avoid that by explicitly processing \n in gowork.install and
translate it to just ' '. This helps people because now gowork.install
becomes just a regular multiline buildout entry, similar e.g. to
gowork.cpkgpath et all.

Here is one example where it helps:

jerome/slapos@95c45fe0 (comment 68408)

/reviewed-by @jerome
/reviewed-on nexedi/slapos!430

Since f427842b some software releases has been
found to be without pinnsed eggs for GitPython dependency.

/reviewed-on !432

This is a backward incompatible parameter change.

for example to run on saucelabs, instead of:
  {
    "target": "iOS",
    "target-version": "11.3",
    "target-device": "iPhone Simulator",
    "target-browser": "Safari",
    "appium-server-auth": "username:auth-token",
    "test-suite" : "renderjs",
    "remote-access-url": "https://softinst1234.host.vifib.net"
  }
we now use:
  {
    "target": "selenium-server",
    "desired-capabilities": {
      "platformName": "iOS",
      "browserName": "Safari",
      "platformVersion": "11.3",
      "deviceName": "iPhone Simulator"
    },
    "server-url": "https://username:auth-token@ondemand.saucelabs.com/wd/hub",
    "test-suite": "renderjs",
    "remote-access-url": "https://softinst106116.host.vifib.net"
  }

To run locally empty parameters are still OK.

/reviewed-on nexedi/slapos!427

/reviewed-on nexedi/slapos!413

using husky + lint-staged

There was two sections writing the file `bin/monitor-httpd` which led to some problems when running things

/reviewed-on nexedi/slapos!426

/reviewed-on nexedi/slapos!409

/reviewed-on nexedi/slapos!411

/reviewed-on nexedi/slapos!410

  Sticky computer on kvm cluster, will make the requester (root instance on this case), request
  the children on the same computer as itself.

/reviewed-on nexedi/slapos!421

usually, the software release path is :
in a web runner : /srv/slapgrid/slappartXX/srv/runner/project/buildout.cfg
in a test node : /srv/slapgrid/slappartX/srv/testnode/xx/inst/test0-XX/srv/runner/project/buldout.cfg

the previous regex was replacing in all slappartX and test0-X by the new test0-Y
which of course would make an existing path : /srv/slapgrid/test0-Y/.../test0-Y/...

This commit only replace the latest occurence in order to have
compatible code in the "normal" case, and in the test nodes