* Improve the wording of the defintion of a Counter

* Link to the wikipedia article on Montonic functions.
* Mention that counters can be reset to zero.
* Change language to speak directly to the user.
Signed-off-by: Ben Kochie <superq@gmail.com>

* Fixup "that can decrease"
Signed-off-by: Ben Kochie <superq@gmail.com>