A new plug-in for working with slave OpenHPI daemon

A concept is proposed where there is a Master OpenHPI daemon instance and a Slave OpenHPI daemon instances.
An HPI User works with the Master OpenHPI daemon.
The Master OpenHPI daemon passes the slave OpenHPI daemon resources as its own.
Of course resource id will be not the same and will be assigned to another value to avoid resource id collision.
Slave plug-in will handle resource id mapping.
Slave plug-in is able to add entity path root to all Slave OpenHPI daemon resources.
Slave plug-in also will handle different HPI structures so this resource id change and entity path change will be
consistent.

How to use:
Just add slave plug-in stanza in openhpi.conf.
An example:

handler libslave {
entity_root = "{SYSTEM_CHASSIS,13}"
host = "192.168.1.139"
}

"port" parameter is also supported.

In this case the Master OpenHPI daemon will represent all resources of Slave OpenHPI daemon running on 192.168.1.139.
All resources' entity paths will be prefixed with {SYSTEM_CHASSIS,13}.

An archive with the patch for build system and the plug-in source code is attached.
How to compile:
Apply patch for build system.
Put plug-in source code to plugins/slave.
Run "./bootstrap"
Run "./configure --enable-slave"
...