Enhances description for event definition. Adds examples of event
use. Enhances descriptions in event API table.
Note: Enhancement of the initial part of this document is left
for future commits.
Change-Id: Ic754daacecbcb2b0ddc6b3a59d0a3b88d622662f
Signed-off-by: Allan Stephens <allan.stephens@windriver.com>