Adding cf-isalive

Per @zzamboni request
See https://groups.google.com/forum/#!topic/help-cfengine/NmyIOyUMLxw
Applied @ediosyncratic suggestions
Merge branch 'master' into cf-isalive
Support for CFEngine 3.6
Updated with latest version
Merge pull request #1738 from lra/cf-isalive

Adding cf-isalive