Rework "--servertickle" option to be easier to use

[todbot]

Currently you do things like:

blink1-tool --servertickle 1,1,5,7

To say "enable servertickle, stay lit on enable, play sub-pattern 5-7". This is pretty hard to parse. We can do better.

[todbot]

e.g.

• You should be able to specify "10m" for 10 minutes (not useful in past firmware, but >= v205"
• separate command-line args for each arg?
• fill out help page
• write doc on this (see blink1-python for a start)