dpdk: Update documentation.

Add usage info for ovs-vswitchd dpdk option. Update
INSTALL.DPDK file and man page.

Reported-by: Hari Sasank Bhamidipalli <hbhamidi@cisco.com>
Signed-off-by: Pravin B Shelar <pshelar@nicira.com>
Acked-by: Ben Pfaff <blp@nicira.com>
Acked-by: Flavio Leitner <fbl@redhat.com>
Packaging: Add useful files for debian and rhel.

CC: Ben Pfaff <blp@nicira.com>
Signed-off-by: Flavio Leitner <fbl@redhat.com>
Signed-off-by: Pravin B Shelar <pshelar@nicira.com>
Acked-by: Ben Pfaff <blp@nicira.com>