Use GtkHeaderBar
This merge request add support for CSD:
- Shell: Move toolbar inside a GtkHeaderBar and move menubar below it.
- EcontactEditor: Same as above
- ECompEditor: Same as above + merge "All day event" behaviour between tasks/events
- EComposer: Same as above + add an option to hide edition toolbar
- EAlertDialog: Use GtkHeaderBar
- EShellSwitcher: Replace icons by symbolic ones
Edited by Milan Crha