Implementing GcalWeekView to match the mockups.

What to say about this commit.
There's just one FIXME in gcal-week-view.c, about the size/width of the
GtkScrollbar used. That should not be hardcoded.
Also the background color applied to the scrollbar through css-theming might be
better placed inside the code, since the effectis part of the view.
About this view is still missing a way of signaling the current day. We are on
it, yet.

data/gtk-styles.css

@@ -40,6 +40,7 @@
 
 .calendar-view header {
   font: bold 12;
+  background-color: @theme_bg_color;
 }
 
 .calendar-view {
@@ -47,6 +48,7 @@
   font: 10;
 }
 
+
 .calendar-view:selected {
   color: #0C73E5;
   font: bold;
@@ -68,6 +70,15 @@
   border-radius: 0;
 }
 
+.scrollbar.slider {
+  background-color: alpha (@scrollbar_slider, 0.5);
+  border: #6e6e6e 1px solid;
+}
+.scrollbar.trough {
+  background-color: transparent;
+  background-image: none;
+}
+
 .entry {
   border-radius: 0;
 }