[Feature] Implemented editing of root timeline start and end dates. Minor updates of datepicker and forms.

Details:
1. Added support of editing start and end dates of root timeline.
2. Now end date is set to infinity in case if timeline's end date is infinity (9999).
3. Little update of forms (added prefix "I" for interface names).
Merge pull request #360 from alex-zen/roottimelineedit

[Feature] Implemented editing of root timeline start and end dates. Minor updates of datepicker and forms.