Let issues work via STI
Fix tests
Handle different change column names
Re-implement watcher deletion
Introduce work unit permissions
Remove unclear test asserts
Introduced default value
Create work_units table migration
Rename time entry's work unit reference
Rename work unit to work package
Rename work unit custom field
Rename migration
Adapt references to work package
Use legacy issue implementation for migration
Rename legacy databases
Merge branch 'feature/rails3' into feature/rails3_sti

Conflicts:
	app/controllers/timelog_controller.rb
	app/helpers/application_helper.rb
	app/models/alternate_date.rb
	app/models/available_project_status.rb
	app/models/default_planning_element_type.rb
	app/models/enabled_planning_element_type.rb
	app/models/planning_element.rb
	app/models/planning_element_type.rb
	app/models/planning_element_type_color.rb
	app/models/project_association.rb
	app/models/project_type.rb
	app/models/query.rb
	app/models/reporting.rb
	app/models/scenario.rb
	app/models/timeline.rb
	app/views/planning_elements/_form.html.erb
	features/issues/issue_edit.feature
	features/step_definitions/timelines_given_steps.rb
	features/step_definitions/timelines_then_steps.rb
	features/step_definitions/timelines_when_steps.rb
	features/support/paths.rb
	lib/timestamps_compatibility.rb
	spec/controllers/timelines_planning_elements_controller_spec.rb
	spec/factories/timelines_planning_element_journal_factory.rb
	spec/models/alternate_date_spec.rb
	spec/models/planning_element_spec.rb
	spec/views/api/v2/planning_elements/_planning_element_api_rsb_spec.rb
	test/integration/api_test/time_entries_test.rb
Fix tests
Fix API test by creating object instead of building
Fix general step
i18n for created_/updated_at