Fix brooklyn-examples dependency on brooklyn-parent.

Users who download the Brooklyn Distro are instructed to try the examples by building them from source.

Unfortunately, as they have not built Brooklyn from source /brooklyn/pom.xml is missing. This breaks the parent dependency in /brooklyn/examples/pom.xml and causes the examples build to fail.

This PR duplicates the relevant sections of /brooklyn/pom.xml in /brooklyn/examples/pom.xml, allowing the examples to be built on their own.

Notes have been added to both pom.xml files to explain why a simple &lt;parent&gt; is not used, and as a reminder that changes to /brooklyn/pom.xml must be duplicated in /brooklyn/examples/pom.xml.