[core] restructure to allow PIP packaging

OK - so I have to admit I *hate* the fact that PIP seems to require a
subdirectory named like the library.

But since the PIP package is something really nifty to have (thanks to
@tony again!!!), I updated the codebase to hopefully conform with what
PIP expects. Testruns so far look promising...

bumblebee_status/modules/contrib/dunst.py

@@ -0,0 +1,37 @@
+# pylint: disable=C0111,R0903
+
+"""Toggle dunst notifications.
+
+contributed by `eknoes <https://github.com/eknoes>`_ - many thanks!
+"""
+
+import core.module
+import core.widget
+import core.input
+
+import util.cli
+
+
+class Module(core.module.Module):
+    def __init__(self, config, theme):
+        super().__init__(config, theme, core.widget.Widget(""))
+        self._paused = False
+        # Make sure that dunst is currently not paused
+        util.cli.execute("killall -s SIGUSR2 dunst", ignore_errors=True)
+        core.input.register(self, button=core.input.LEFT_MOUSE, cmd=self.toggle_status)
+
+    def toggle_status(self, event):
+        self._paused = not self._paused
+
+        try:
+            if self._paused:
+                util.cli.execute("killall -s SIGUSR1 dunst")
+            else:
+                util.cli.execute("killall -s SIGUSR2 dunst")
+        except:
+            self._paused = not self._paused  # toggling failed
+
+    def state(self, widget):
+        if self._paused:
+            return ["muted", "warning"]
+        return ["unmuted"]