Added container virtual object.
Example plug-in.
split headers in public and private

public headers are meant to be available to plugins, so
they must be
1. minimal
2. ABI stable, or at least ABI forward-compatible.
port to new plugin API/ABI

and implement the plugin loader along the way
logger has to be part of the public interface.
update for the logger API
nitpicks
nitpicks /2
avoid void * in interface /1
nitpicks
add printf-like helper in responsewriter
http_parser is embedded now
cleanup. More adheren to coding style.
cleanup. More adherent to coding style.
modules are cmake modules not shared libraries.
Merge branch 'feature/plugins-interface-NAPI' into develop