(cherry picked from commit 46abf99483ce8d8dac9b66ddbeb0c85533552514)

When initializing a widget, the template is processed before the
construct properties. That's usually fine, but showing a toplevel
window has the side effect of realizing it; doing that before the
window is associated with an application means that properties like
the GTK application ID won't be exported, and gnome-shell fails to
match the window to the correct .desktop file as a result.

Just remove the property from the template, the code already handles
showingi the window.

See https://gitlab.gnome.org/GNOME/gnome-shell/-/issues/2893

There's a pretty good chance that there were some changes in
evolution-data-server since `1.13`, so let's bump it to a reasonable
minimum by setting it to the one in Debian stable (which is 3.30)

We started requiring at least version 2.52 when we started using
`Uuid.string_random()` (thanks @ricotz for pointing this out).

Let's just immediately bump it to the currently supported version of
Debian stable, which is 2.58.

@ricotz helpfully pointed out that we don't need the
`--disable-since-check`, since we don't even compile on valac 0.38.10.

Let's remove the check for the option, and instead have a check at the
beginning that people aren't trying to compile Contcts on a too old
Vala.

* Remove `using` for all namespaces (except Folks)
* Rename some variables
* Add `this.` to instance variables

Whoopsydaisy

Just use `dialog.run()`

This gives us a consistent style, which allows us to install an
automatic review step for style consistency using a formatter.

Only elevate Folks to the primary namespace.

The current code that created a new window was a mess, and didn't really
say what or why we were doing things. This commit cleans up some of this
by renaming some variables and functions and making sure we always show
a window to the user, so that we can provide useful feedback.

... and fix the minimal height obscuring most of the content on
non-small screens.

Fixes https://gitlab.gnome.org/GNOME/gnome-contacts/-/issues/119

* Properly catch an error when unlinking
* Removed unused `using Gtk` statement
* Prefix instance variables with `this.`
* Don't use `error()` which will abort the application

* Fix warning
* Remove unnecessary `using` statements
* Add `this.` prefix for instance variables

We've had compilation errors thanks to that before, when libhandy
introduced a similar name as that of Gtk (e.g. HdyHeaderBar vs
GtkHeaderBar). It also makes grepping a bit easier for maintainers :-)

This shouldn't have been merged in, and is now giving warnings. Let's
remove it for now, and if somebody still needs it, they can use the Git
history for that.

We've had compilation errors thanks to that before, when libhandy
introduced a similar name as that of Gtk (e.g. HdyHeaderBar vs
GtkHeaderBar). It also makes grepping a bit easier for maintainers :-)