Related new task dialog

[acetousk]

When wanting to add a Task related to the current Task, the current work flow is:
Start at the EditRelated screen for Task 1

1. Go to FindTask
2. Fill out the Create Task Dialog (create Task 2)
3. Find Task 1 in Find Task
4. Go to EditRelated screen
5. Fill out the Add Related To Dialog (relate Task 1 to Task 2)

This PR's contribution is to add a button for doing this with one dialog where the work flow is:
Start at the EditRelated screen for Task 1

1. Fill out the Create Related To Task (create Task 2 and relate Task 1 to Task 2)