Collective.documentgenerator

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- Added upgrade step to `14` that will add the `oo_port_list` parameter to the registry.
[gbastien]

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- Use appy to load balance on multiple LO server.
[odelaere]

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- Added `iterable_in_columns` (for labels document).
[sgeulette]
- Added `get_relations` in dexterity
[sgeulette]
- Use Appy to search and replace in POD templates pod expressions.
[aduchene]
- .ods POD Templates are now usable with search and replace.
[aduchene]
- Make sure tmp directory is unique when searching and replacing.
[aduchene]
- Updated readme
[Arhell]

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- Method update_oo_config updates all the registry entries for libreoffice server.
[odelaere]
- Added subscriber to update oo config on process start.
[odelaere]

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- Added helper `ConfigurablePODTemplate.get_filename` to easily get file filename.
[gbastien]

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- Updated metadata version.
[sgeulette]