Maven cleanup and features-parent migration

Maven cleanup and features-parent migration

Use features-parent {{VERSION}} to allow dropping a number of Maven
properties.

Upgrade commons-collections (1.0 -> 3.2.1) and httpcomponents (4.2.1
-> 4.4.1).

Drop a number of obsolete components from dependency management
(controller:commons.northbound, controller:containermanager,
controller:forwardingrulesmanager, controller:sal,
controller:switchmanager.

Use odlparent-provided versions of commons-lang3, most netty
components, and the equinoxSDK381 components.

Drop obsolete io.netty:netty:3.8.0 dependency (replaced by
io.netty:netty-all in versions 4+).

Remove some duplicate dependency declarations.

Use "<relativePath/>" instead of "<relativePath></relativePath>" now
that it's safe to do so (the auto-release scripts handle it).

Change-Id: I62a385ba49d79e045934ec706f69313425553ae0
Signed-off-by: Stephen Kitt <skitt@redhat.com>