Insert key as shortcut for inserting entry

This commit adds an alternative shortcut for Ctrl-+ to insert a new time
entry. Ctrl-+ is cumbersome on some keyboard layouts where it requires
multiple modifiers (Ctrl, Shift) to be pressed simultaneously.  Pressing
a single key instead of performing a two-hand finger gymnastics exercise
on these layout may be preferrable for some users.

Signed-off-by: Hynek Mlnarik <5391360+hmlnarik@users.noreply.github.com>

Author: hmlnarik

po/fr.po

@@ -305,7 +305,7 @@ msgstr "_Arrêter le suivi"
 
 #: src/hamster/overview.py:94
 #, fuzzy
-msgid "Add activity (Ctrl-+)"
+msgid "Add activity (Insert, Ctrl-+)"
 msgstr "Ajouter une activité"
 
 #: src/hamster/overview.py:100

src/hamster/overview.py

@@ -88,7 +88,7 @@ def __init__(self):
         self.add_activity_button = gtk.Button()
         self.add_activity_button.set_image(gtk.Image.new_from_icon_name(
             "list-add-symbolic", gtk.IconSize.MENU))
-        self.add_activity_button.set_tooltip_markup(_("Add activity (Ctrl-+)"))
+        self.add_activity_button.set_tooltip_markup(_("Add activity (Insert, Ctrl-+)"))
         self.pack_end(self.add_activity_button)
 
 
@@ -500,6 +500,8 @@ def on_key_press(self, window, event):
         elif event.keyval == gdk.KEY_Right:
             self.header_bar.time_forth.emit("clicked")
             return True
+        elif event.keyval == gdk.KEY_Insert:
+            self.start_new_fact(clone_selected=True, fallback=True)
 
         if self.fact_tree.has_focus() or self.totals.has_focus():
             if event.keyval == gdk.KEY_Tab: