/reviewed-on !269

Fix error display after save
Fix parameters not recognized
Fix python linting
the same way as ERP5 Script Python

Models with workflow state "default" are only considered in composition if no
other valid model is defined. This allows to implement "ingest anything"
policy in wendelin.

Add PortalType field to distinguish different types of Python Scripts, add referencence and use source code editor

zope.{interface,component} implement Interfaces through __implements__,
__implemented__ (both implementedBy instances) and __provides__ (ClassProvides
instance) attributes set on the class itself through implementedByFallback
(zope.interface.declarations).

However, this implementation creates circular references by referencing the
class itself and thus erp5.* classes (and all its Accessors instances) were
never GC even after a reset.

When running testXHTML and installing the Unit Tests bt5s:
  * After 10 resets:  21MB leak (~  7% of Zope process USS).
  * After 20 resets:  70MB leak (~ 18% of Zope process USS).
  * After 28 resets: 122MB leak (~ 26% of Zope process USS).

Fixes browsing ERP5 documents without activity tables available.
Of course, as most modifications trigger activity creation, no
modifications are possible. But this improves read-only access in
degraded conditions.
Also, by design a successful query must return one line, so do not test
returned value before processing it.