Changes to speed up opening messages in view and editor

Changes to speed up opening messages in view and editor
* src/maemo/modest-msg-edit-window.c:
        * Do the show all of edit window construction to make it
          feel a bit faster.
* src/maemo/modest-msg-view-window.c:
        * Show all early to feel faster.
        * Dimming rules should be evaluated after being visible, not
          before.
* src/modest-ui-dimming-rules.c:
        * Make clipboard checks for GtkHtml be avoided when the
          selection is empty.

pmo-trunk-r3931