Adapts changed AAJ interface
Adds association to Journal
Introduces journable

Journable introduces a connection between a journal and the journalized
object.
Fixes functionals

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Merge branch 'feature/normalize_acts_as_journalized' of github.com:opf/openproject into feature/normalize_acts_as_journalized

Conflicts:
	app/models/planning_element.rb
	app/models/work_package.rb
	lib/plugins/acts_as_activity_provider/lib/acts_as_activity_provider.rb

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