Documentation improvements in includes/actions

- Separate file and class documentation
- Add some missing class documentation
- Fix erroneous documentation

Change-Id: I35c846ad63e837165b79456dc89d330498aebf64
Don't use isset() to check whether an existing variable is null

Change-Id: Ie63f060fb7928fd51a8ad71293955f923f6a18c3
Merge "Don't use isset() to check whether an existing variable is null"
Merge "Documentation improvements in includes/actions"