Collective.documentgenerator

----------------

- Extend the base helper view to do plone, plone_portal_state view available
and added a method 'translate' to be able to translate a msgid in a given domain.
[gbastien]
- Refactored the DocumentGenerationHelperView.display_date method to use
toLocalizedDate and adapted AT and DX implementations.
[gbastien]
- Refactor the generation view to pass the arguments `pod_template` and `output_format`
directly to the view call or its methods.
[gbastien, sdelcourt]

----------------
- Renamed field `pod_portal_type` to `pod_portal_types` as this field
is a multiselection field.
[gbastien]
- Renamed `doc_uid` parameter used by the `document-generation` view to
`template_uid`, more obvious, and makes it available in the viewlet
link infos dict.
[gbastien]
- Added field IConfigurablePODTemplate.pod_formats to be able to select the
format we want to generate the POD template in.
[gbastien]
- When evaluating the tal_condition on the template, pass extra_expr_ctx
to the TAL expression so `context` and `here` become the element on which the TAL
expression is actually evaluated instead of the pod_template and `template`
is the pod_template
[gbastien]

----------------
- Initial release.
[gbastien]

- ...

- Update bootstrap
use https://raw.githubusercontent.com/buildout/buildout/master/bootstrap/bootstrap.py
[fngaha]