Add wayland socket name to container configs

A Unix socket is used by wayland compositor in the multi-process mode to communicate between various windows. When starting the QtApplication manager, a name for the Unix socket is passed as a command-line argument.  

This socket name is needed when setting up a container, basically, to create a file bind mount into the container. Allowing containerized the appman-launcher-qml process to access the wayland.

Ex. Usage of wayland socket when creating a container

https://github.com/Pelagicore/softwarecontainer/blob/master/libsoftwarecontainer/src/gateway/waylandgateway.cpp#L75

The problem with the above approach is the socket name has should be known when starting the softwarecontainer-agent.

Proposed solution:

Instead of passing the socket name via an environment variable when starting softwarecontainer, pass it via an IPC(DBus) call dynamically.

To do this, the socket name should be available to the container plugin.

This can be done easily using the `setConfiguration` function in `manager-lib/containerfactory.h`

See the attached patch for the proposed solution.