Switch to more traditional logging structure

Init a shared log instance in virtinst/logger.py, and use that
throughout the code base, so we aren't calling directly into
'logging'. This helps protect our logging output from being
cluttered with other library output, as happens with some
'requests' usage

virtManager/manager.py

@@ -4,13 +4,12 @@
 # This work is licensed under the GNU GPLv2 or later.
 # See the COPYING file in the top-level directory.
 
-import logging
-
 from gi.repository import GObject
 from gi.repository import Gtk
 from gi.repository import Gdk
 from gi.repository import GdkPixbuf
 
+from virtinst import log
 from virtinst import xmlutil
 
 from . import vmmenu
@@ -69,7 +68,7 @@ def _get_inspection_icon_pixbuf(vm, w, h):
         pb.close()
         return pb.get_pixbuf()
     except Exception:
-        logging.exception("Error loading inspection icon data")
+        log.exception("Error loading inspection icon data")
         vm.inspection.icon = None
         return None
 
@@ -182,7 +181,7 @@ class vmmManager(vmmGObjectUI):
         if vis:
             return
 
-        logging.debug("Showing manager")
+        log.debug("Showing manager")
         if self.prev_position:
             self.topwin.move(*self.prev_position)
             self.prev_position = None
@@ -193,7 +192,7 @@ class vmmManager(vmmGObjectUI):
         if not self.is_visible():
             return
 
-        logging.debug("Closing manager")
+        log.debug("Closing manager")
         self.prev_position = self.topwin.get_position()
         self.topwin.hide()
         vmmEngine.get_instance().decrement_window_counter()