Handle PFCP processing by separete core

[korroot]

Introduce multi-core support by separating PFCP processing from data packet processing

[sergeymatov]

By design PFCP served on main core of VPP. To have core affinity for pfcp and user data cores for serving UP traffic should be specified in startup. Main core should also be specified in startup config.
To configure separate workers for data processing, workers should be defined for cpu section of startup config
To configure dedicated main-core for PFCP processing, main-core should be defined for cpu section as well
cpu { main-core <X> workers <N> }
However there is an issue #185 blocking this functionality