Helps developing valid software release descriptors.
Allows checking instance parameters and published values against a software
release's schema in addition to validating the schemas themselves against
slapos' schema.json and jsonschema's schemas.

Also, describe a bit more "serialisation" override mechanism: these
properties cannot be made required at schema level, but for any
software-type entry a serialisation must be provided.

it is required for DBD-mysql-4.0.42 with MariaDB 10.1.

This simplistic mail setup does not pass address as command line arguments,
so it is not subject to the vulnerability protected against by this option.

See https://jira.mariadb.org/browse/MDEV-12950 for API changes.

Because this does not seem to be enough:
https://github.com/perl5-dbi/DBD-mysql/pull/133

We should keep using MariaDB 10.1 for ERP5 as long as perl-DBD-mysql
is not fixed properly.

  The version 2.2.0 depends on PyNaCL which is not well configured currently on buildout.

@Tyagov @luke 

This MR adds the following to all Jupyter notebooks:
 - A warning when a user inputs a reference that has already been used in one of his old Jupyter notebooks. 
 - Some extra information when entering magics such as the remaining required magics.
 - Entering the reference MUST now be the last magic entered(otherwise the reference check doesn't work).
 - A small addition to the message at the top of the notebook for the command ```%notebook_set_title```

Also, do note that the edited kernel uses files from [this commit](nexedi/erp5@4a3e5173) from my erp5 repo, so the changes there must be available for the kernel to work. [This merge request](nexedi/erp5!283) addresses those changes.

Sample screenshot:
![Screenshot](/uploads/a34e0b70b991302539c572ad4344ba56/Screenshot.png)


/reviewed-on nexedi/slapos!177

/reviewed-on !157

/reviewed-on nexedi/slapos!166

@Tyagov  @kirr 

/reviewed-on nexedi/slapos!171

Buildout commit in discussion:  nexedi/slapos.buildout@43839169

/reviewed-on nexedi/slapos!176

  Follow up the change done on boost-lib: 'component/boost-lib: build with SlapOS gcc.'
  Include --with-boost on configure.

  Use  /folder/script can lead to mistakes which cause error, as
  the instance side cannot find the file. Use directly the section is better to ensure
  you get the file even after changes on common.cfg.

  Clean up location set on common.cfg, and reduce code duplication.