Added include file dpdk.inc to share common functionality based on
dpdk_1.6.0r2

Added a new variable EXAMPLE_BUILD_DIR. this points to apps build
directory which is different in dpdk v1.6.0r2 and v1.7.0.
Users of dpdk.inc have to define EXAMPLE_BUILD_DIR for the
installation of example apps.

Signed-off-by: Sreeju Selvaraj <sreeju.armughanx.selvaraj@intel.com>
Acked-by: Ong Boon Leong <boon.leong.ong@intel.com>
Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>