script related improvements

[jkroonza]

Based on #586:

• Fixed the sample scripts for auth-*.
• Documented all the *-script options that was already in place (8 of them).
• Implemented and document auth-{up,down}-script override options (and documented).

[cd-yangling]

Fantastic. @jkroonza's turnaround speed exceeded my wildest expectations. My thanks again for your work.

[Neustradamus]

@jkroonza: Thanks for your work and thanks to @paulusmack for merging!