the Redis backend supports UNIX, TCP and custom ports
no real transactions nor iteration, but it’s not needed at the moment
transactions keep replies in a freelist, which is purged on transaction
commit / abort

also some cleanup and version bump to Q2

extracted part about writing layers to lib documentation

The engine is responsible for central managemento of resources and work
distribution. This allows to spawn multiple loops.

The engine configuration / interface is based on Lua 5.1-5.2, including
a RPC and a simple CLI interface. This is going to be the core of configuration
later on.