Task-030 Implement failing validations on project follow up

[manoutbar]

• [x] Validation between task workload and execution period on create and update
• [x] Validation between public/private workplan and public/private tasks updating
• [x] Validation at tasks deletion which are linked with some work plan
• [x] Remove prefilling shout form
• [x] Add more sample data (at least 6 items per list)
• [x] Include back button in work plan tasks list
• [x] Include all translation keys in work plan task views

[manoutbar]

i have needed 3.5 to complete this task