Fix : sip protocol handlers on Windows and add support to tel and callto...

Fix : sip protocol handlers on Windows and add support to tel and callto protocols on Windows/Linux/Mac
- Replace app-icon by a specific windows file that describe the application properties
- Add Windows Description file
- Update NSIS Installation/Uninstallation to support handlers (sip, sip-linphone, sips, sips-linphone, tel and callto)
- Cleaner use of Windows registries