Introduce new classes for client-server communication.

Still based on what we had already, though more separated.
Change-Id: I4cce298003a4ffc2ebcec01fea1a07adfbfdf990
Reviewed-by: Tim Jenssen <tim.jenssen@digia.com>
Reviewed-by: Niels Weber <niels.weber@digia.com>
Replace client-server classes and update implementations.

Remove superfluous file engine tests. Introduce auto test
for newly added client server classes. Fix some wrong
implementations serverside for settings array handling and
broken arguments in process wrapper. Replace all other parts
that with new implementations. Remove now unused classes.
Change-Id: I6f9e836993096a2c2c06b06f2b06d7aa4b287e56
Reviewed-by: Tim Jenssen <tim.jenssen@digia.com>