Fix GTK default keybindings being still active after being unbound

If we provide an AccelGroup when creating a menu item using a sock ID,
it installs the GTK default accelerator, accelerator we can't remove
since we don't know about it.  So, don't give an AccelGroup so GTK
don't install it's own accelerator.

This fix also required to properly update the accelerator on some item
we used to ignore since the update didn't work anyway (since the GTK
accelerator was displayed instead).

Note that this doesn't fix the fact the editor popup menu accelerators
are never updated after startup so they don't get updated before
restart after changing a keybinding in the preferences.  This is a
separate (and less problematic) issue due to a simple lack of update.

Closes #1912683 and #3599251.
Allow Quit keybinding to be configured

This removes the last unmodifiable keybinding relying on GTK's
defaults, and allows somebody to change this keybinding.
Adjust Terminal tooltip in preferences

Adjust to say it is a full command and that %c is substituted by
the geany_run_script path.
Merge branch 'master' of https://github.com/geany/geany
Add missing slash in default command
More verbose update to manual for Terminal setting

Provide a more complete description of the use of the changed
Terminal setting in several places.
Update the main.d template to use a more standard prototype for main()
Fix plugin_add_toolbar_item insertion order
Update NEWS for new items
Update of Hindi translation
Update of po-files for string freeze of Geany 1.23
Update of Japanese translation
Update of French translation
Update of Lithuanian translation
Update of Spanish translation
Correct description of build_activate_menu_item()

Correct the documentation comment for build_activate_menu_item() for
plugin documentation.
Fix comment toggling in PHP and HTML with bottom-up selection

If current position is not at selection start (e.g. bottom-up
selection), editor_get_filetype_at_current_pos() will start returning
improper result as soon as the first buffer change since the style at
the actual current position will have been invalidated and not yet
recomputed.
Update of Galician translation
Update of Slovenian translation
Update of Italian translation