Remove Canvas* widgets and other hippo-canvas using parts

hippo-canvas isn't available in the GTK3 world, so we need to remove
anything that depends on it. Activities that still use it will need replace
hippo-canvas based widgets with native GTK ones before they can be ported to
GTK3.

[replaced description]
Signed-off-by: Sascha Silbe <silbe@activitycentral.com>

tests/graphics/hipposcalability.py

@@ -1,51 +0,0 @@
-import hippo
-import gtk
-import gobject
-
-from sugar3.graphics.icon import CanvasIcon
-from sugar3.graphics.roundbox import CanvasRoundBox
-
-import common
-
-test = common.Test()
-
-canvas = hippo.Canvas()
-test.pack_start(canvas)
-canvas.show()
-
-scrollbars = hippo.CanvasScrollbars()
-canvas.set_root(scrollbars)
-
-box = hippo.CanvasBox(padding=10, spacing=10)
-scrollbars.set_root(box)
-
-
-def idle_cb():
-    global countdown
-
-    for i in range(0, 100):
-        entry = hippo.CanvasBox(border=2, border_color=0x000000ff,
-                                orientation=hippo.ORIENTATION_HORIZONTAL,
-                                padding=10, spacing=10)
-
-        for j in range(0, 3):
-            icon = CanvasIcon(icon_name='go-left')
-            entry.append(icon)
-
-        for j in range(0, 2):
-            text = hippo.CanvasText(text='Text %s %s' % (countdown, j))
-            entry.append(text)
-
-        box.append(entry)
-
-        countdown -= 1
-
-    return countdown > 0
-
-countdown = 1000
-gobject.idle_add(idle_cb)
-
-test.show()
-
-if __name__ == '__main__':
-    common.main(test)