New feature: Shortcuts configuration in the GNOME client

SFLphone GNOME client now supports X11 keyboard symbols shortcuts configuration. It is available from snapshot20100304.

Configuration can be set for the following actions:

• Pick up calls, or creating a new one
• Hang up calls
• Display the window in foreground or popup from system tray

More information about the remaining tasks on the wiki: https://projects.savoirfairelinux.com/issues/show/2916.