Read ODP configuration from VPP startup config

Read ODP configuration from VPP startup config

  1) Allow to setup size of allocated memory, number of packets in the
     pool, number of packets in transmit burst and delay in scheduler
     mode from VPP startup file.
     More details are in template: src/vpp/conf/startup.conf
  2) Separate Rx mode from Tx mode. Traffic Manager is not supported.
  3) Devices defined in VPP startup are automatically created at start.

Change-Id: I1f8a3c2900f56cb23ce6997d311cfe55e1c2078c
Signed-off-by: Michal Mazur <[email protected]>