Collective.documentgenerator

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- Added missing upgrade step after registry modification (`force_default_page_style_for_mailing`) in 3.36.
[sgeulette]

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- Bugfix: page style check now handle case of POD template without mailing template
attribute.
[sdelcourt]

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- Add a new parameter `force_default_page_style_for_mailing` to the registry.
If set to True, apply automatically a default page style to mailing templates.
[sdelcourt]
- Order templates directories by title in `dg-templates-listing` view.
[sgeulette]
- Improved `DXDocumentGenerationHelperView.get_value` by adding optional obj parameter.
[sgeulette]

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- Group link by template title.
[odelaere]
- Added 'title' attribute to generation link.
[odelaere]
- Aliased import to avoid confusion.
[sgeulette]
- CSS for generationlinks so it may be adapted more easily.
[gbastien]

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- Stored `template_uid` on a persistent generated document to know which template has been used.
[sgeulette]

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- Added character escaping to avoid xss in `TemplatesTable`
[sgeulette]
- In `utils.update_oo_config_after_bigbang` don't fail instance start up if
`update_oo_config` raises an exception.
[odelaere]