Now that we are requiring at least GTK+ 3.22, we can remove the shortcuts
help from the manual so we aren't duplicating the information with the
Gtk.ShortcutsWindow.
Some remarks:
* Note that Meson adds a hard dependency on Python 3.
* All dependencies and defines are now listed together.
* Some build files were put in their respective subdirectories, e.g. the Geary
engine library will be built from the Meson file in `src/engine`.
* `--fatal-warnings` is no longer an explicit flag, as Meson provides
`-Dwerror=true` for this.
* An explicit resource file needs to be used. The issue to support this from
Meson itself can be found at https://github.com/mesonbuild/meson/issues/706 .
* The `gnome.yelp()` function parses a LINGUAS file so we no longer need to keep
track of all languages in our build system.
* There are no Debian scripts defined in the meson.build files to keep them
clean, but they can be kept as separate scripts in `build-aux`.
* Left out the `dist` target as there is now `ninja dist`
* `geary-docs` is disabled by default, as valadoc-0.38.3 returns errors.
https://bugzilla.gnome.org/show_bug.cgi?id=777044
* help/C/shortcuts.page: Document new shortcuts.
* src/client/application/geary-controller.vala: Add shortcuts for copy
and move actions.
* src/client/components/pill-toolbar.vala (PillBar::create_menu_button):
Hook up the button's related action to invoke the button's popup menu,
taking care not to cause an infinte loop.
(PillBar::setup_button): Connect to the related_action's tooltip notify
signal via a local variable rather than via the button, so it does not
get lost when it changes for Gtk.MenuButton actions.
Namely, the "Use three pan view" and "Always watch for new mail"
options. Also update the text about notifications to reflect changes to
GNOME Shell.
https://bugzilla.gnome.org/show_bug.cgi?id=749925
