Clarify desired location of copyright notices in cmake modules

[osrf-migration]

Original report (archived issue) by Steve Peters (Bitbucket: Steven Peters, GitHub: scpeters).

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In my haste to merge pull request #1, there were some comments that didn't get fully resolved:

• variable for enabling / disabling testing

• location of copyright notice in a module

@mxgrey can you take one more look at these comment threads?