Port doesn't spawn new process for each packet by default

If the linc environment variable sync_routing is set to false, spawn a
new process to route a packet. If it's set to true (or not defined)
stay in parent process.
Issue #5 - Default configuration variable added

Configuration variable with default value added to sys.config.orig and
config_gen script.
Merge pull request #287 from khetzl/issue5

Sync routing

This closes FlowForwarding/LINC-Switch#5.