Checkbox group (parent/children) functionality. Makes a checkbox parent of other checkboxes.
- If the parent is clicked the children are checked/unchecked based on the parent.
- If all the children are checked, parent gets checked too.
- If there is an unchecked item in the children and if the parent is checked, it gets unchecked.
childrencan be a function. In this case, that function is run agaist the parent in order to find the children. This is useful for groups of checkboxes.
- Checks/unchecks parent based on the initial status of its children at start.