Allows requesting a caucase partition and reusing an existing caucase instance.
For client-certificate-based authentication, client must be able to access backend
directly (frontend is not possible).

See !193's comments.

/reviewed-on nexedi/slapos!194

@luke @Tyagov 

When SlapOS launches services they don't have their locale set. This was causing problems with unicode characters in Jupyter notebook names. For example, calling the notebook "Ł" crashes Jupyter's kernel. Hardcoding the UTF-8 locale to the ipython_notebook script fixes that but we should look into making a generic fix for any other services that might have this issue in the future.

/reviewed-on nexedi/slapos!193

/reviewed-on nexedi/slapos!191

Sometimes, glib is only used as a dependency of pkg-config,
which means it's not used by the instantiated services.

So do not force building Python if slapos.rebootstrap is not used.

The slapos master use different instance-erp5 and instance-balancer than erp5 software release. So I included the monitor changes there as well to fix the issue 

/reviewed-on nexedi/slapos!189

IPYTHONDIR was usable for old versions of ipython, but since project was
renamed to Jupyter the environment variable is JUPYTER_CONFIG_DIR.

Ref:
http://jupyter.readthedocs.io/en/latest/projects/jupyter-directories.html#envvar-JUPYTER_CONFIG_DIR

/reviewed-on nexedi/slapos!188

@luke @Tyagov 

In Jupyter notebooks users could enter the url of their `Base_executeJupyter` function, but [it now gets filled in automatically](https://lab.nexedi.com/nexedi/slapos/blob/2f2a5ad0/software/ipython_notebook/template/ERP5kernel.py.jinja#L10). This makes the `%erp5_url` magic redundant which is why we can remove it. This commit also removes all mentions of `%erp5_url` in the kernel output and `custom.js`.

/reviewed-on nexedi/slapos!185

In the NEO SR, this fixes the permission of the downloaded runTestSuite
template.

Parameters not ready for stabilisation yet

The parameters not ready for stabilisation yet
This reverts commit 1db0265cb5f186775ada977e170eb6168b4e7262.

Add functionality to wrapper to ask for an exclusive CPU core.

/reviewed-on nexedi/slapos!184

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.