Server layering

[romangg]

Motivation

After the server-side objects representation is remodeled by #14 more work can be done on the overall structure of Wrapland's server library.

This has the following goals:

• No Qt-usage in deeper layers, modern C++ only.
• Allow different facades for different styles of usage (Qt-like signals/slots, template-based with libsigc++)

Overview

Approach

Create a first prototype as we did with the objects remodel:

• Add Qt facade.
• Move out classes one by one.
• Remove Qt-usage in middle layer in parallel.