The path of the python executable used by an instance was parsed from
the shebang of its software release's bin/buildout. But when the path
is too long, the shebang is just /bin/sh and the script starts with
`exec <executable>`.

See merge request nexedi/slapos.core!516

Improve hateoas support to show shared instances.

It turns out that ERP5 returns
```
'form_id': {
  'type': 'StringField',
  'key': 'form_id',
  'default': 'InstanceTree_viewAsHateoas',
},
```
for the `form_id` in hateoas, so adapt the proxy to do the same.

Currently hateoas support in proxy only lists non-shared instances,
so this always says that the instances are not shared.

See merge request nexedi/slapos.core!511

See merge request !514

   Set it non-editable

See merge request nexedi/slapos.core!513

See merge request !509

   This script isnt used at all

See merge request nexedi/slapos.core!504

   Strict returns directly a single Software Release for a giving url.

   This fast input option aims to allow certain sites, request "related" slaves
   from an Instance Tree.

   The script  InstanceTree_getFastInputDict is used to custom the feature to
   specific software releases, since depends which one is used, and it cannot
   be generalized for now.

See merge request nexedi/slapos.core!505

See merge request nexedi/slapos.core!506

See merge request nexedi/slapos.core!508

See merge request nexedi/slapos.core!507

   In this way, the debug becomes easier to be notified.