* No longer hook it as child of TaskArchitecture. No migration needed
  since this has not been in an official release.
* TimingSpecification references a list of IProjectRoot elements for
  which it provides timing requirements.
* getPeriod() and setPeriod() eOperation in ISamplingPort (and derived
  task and partition ports) as well as Task must be provided with a
  TimingSpecification since - in principle - multiple
  TimingSpecifications can exists in a project
* Adapt PeriodMigrationProvider accordingly
* Add model element handler (and icon) for TimingSpecifications

Issue-Ref: 3470
Issue-Url: https://af3-developer.fortiss.org/issues/3470



Signed-off-by: Simon Barner <barner@fortiss.org>