Fix empty icons by forcibly rescanning the theme

initial scrolling support (non-smooth)

It seems that it's safe to ignore smooth scrolling, so this only
implements the non-smooth version for now.

test/statusnotifieritem.py: Test app for SNI (Qt)

test/appindicator.py: AppIndicator app for testing

AppInd. "convention": accept paths for IconName

It is not intended for apps to set paths as icon name. Some do it
anyway, and some hosts accept it. snixembed now does so too.

fix: virtual signal without implementation (#12)

Only lead to compile errors on earlier valac (0.48.6).

version 0.3.1

See tag for announcement.

improve new_icon handling (less buggy, more async)

handle non-null but empty icon_pixmap

version 0.3.0

See tag for announcement.

logging: ignoring reregistration now not a warning

makefile: do not require git

We will now only use git if .git/HEAD is found, otherwise the version
info is pulled from version.vala as is.

INFO: electron supports XEmbed tray icons again!

See https://github.com/electron/electron/pull/23674. This means
snixembed is of limited use for now, if you are running the latest
electron version.

async: track IconThemePath updates again

Fixes ~steef/snixembed#5 as far as we can (old node versions still send
nonexisting IconThemePaths sometimes, so icons may still break).

ignore empty icon names

README: link to Void package by projectmoon

README: known issue: gtk_widget_get_scale_factor

This could mean no XEmbed tray is present. Thanks to projectmoon.

StatusIcon: set name after it exists

Apparently Gdk raises a critical error if a name is set before an icon
is set, maybe the window is not yet created at this point. See
https://github.com/dorkbox/SystemTray/issues/19 for context.

code quality, notably spaces for indentation

This is horrible for git blame and whatnot, but luckily I'm always to
blame so far. Better now than later.

mention powerman's ebuild