Add rendering of server-side cursor locally

This adds handling of cursor shape received from server.
This allows us to show same cursor locally.

If local cursor is requested/disabled, server is reconfigured with proper
encodings to enable/disable support for sending it.

If server does not support sending local cursor,
default Qt cursor is shown as a fallback.

Note: sometimes VNC server does not support changing from
sending local to showing remote cursor and this causes slight delay
due to reconnect.