Update ZED copyright boilerplate

Update ZED copyright boilerplate

This commit updates the copyright boilerplate within the ZED subtree.

The instructions for appending a contributor copyright line have
been removed.  Manually maintaining copyright notices in this
manner is error-prone, imprecise at a file-scope granularity, and
oftentimes inaccurate.  These lines can become a pernicious source of
merge conflicts.  A commit log is better suited to maintaining this
information.  Consequently, a line has been added to the boilerplate
to refer to the git commit log for authoritative copyright attribution.

To account for the scenario where a file may become separated from
the codebase and commit history (i.e., it is copied somewhere else),
a line has been added to identify the file's origin.

http://softwarefreedom.org/resources/2012/ManagingCopyrightInformation.html

Signed-off-by: Chris Dunlap <cdunlap@llnl.gov>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #3384