Introduced environment variables:
* EMPER_WORKER_COUNT: specifies how many worker the Runtime default constructor
                      starts.
* EMPER_PINNING_OFFSET: specifies the cpu id where the workers should be pinned
                        round robin.

Both variables allow multiple emper processes to run on the same system
by splitting the available cores.

EMPER_WORKER_COUNT=1 build/apps/echoserver &&
EMPER_WORKER_COUNT=1 EMPER_PINNING_OFFSET=1 build/apps/echoclient

Starts a single threaded echoserver on core 0 and a single threaded
echo client on core 1.