Rework pkgng detection.
Fix typo.

Reported by:	Creaky <whatexercise@gmail.com>
Add support for source+ syntax.

Appending a plus sign + after the source ports tree name will execute
copy_to and copy the contents of the source ports tree into the target
ports tree tree without considering versions.
Modernize poudriere ports tree locations.

Once uppon a time, poudriere required ZFS and stored it's ports trees
into /usr/local/poudriere/ports/${_poudriere_tree}/ports.

Nowadays, poudriere places managed ports into
/usr/local/poudriere/ports/${_poudriere_tree}

This is an attempt to make ZFS and non-ZFS users happy.
Bump VERSION to 1.0.10.