* src/maemo/modest-msg-edit-window.c: added support for rich editing

* src/maemo/modest-msg-edit-window.c: added support for rich editing
  (using wpeditor library).
        * Includes support for toggling bold/italics, adding bullet lists,
          inserting images, changing font color, size and face.
* src/maemo/modest-icon-names.h:
        * Added icon for bullet lists in edit window.
* src/gnome/modest-icon-names.h:
        * Added icon for bullet lists in edit window.
* src/maemo/ui/modest-msg-edit-window-ui.xml:
        * Added menu formatting actions (inserting images, alignments, background
          color, bullet lists).
        * Added toolbar formatting actions (bold, italics, bullet lists), and
          a place holder for font properties elements in toolbar.
* src/maemo/ui/modest-msg-view-window-ui.xml:
        * Added menu actions for messages (not implemented yet, includes replying,
          deleting, and others.
* src/gnome/modest-msg-edit-window.c:
        * Modified methods to send mail to support the new API supporting rich text
          editting. Anyway the Gnome client does not support this yet.
* src/widgets/modest-mail-header-view.[ch]:
        * Now date/time field separates the Time: value as a new field, and it's
          always shown independent from being a mail sent another day.
        * Preliminar support for showing priority icons in subjects. Now subject is
          showin as a GTKHBox, with a first part for priority icon (currently not used)
          and a second part for the subject itself.
        * Changed order of header fields (recipients in special) to accomplish the
          UI specs.
        * Added new method to add custom headers (header data implemented with a widget).
          This is used for adding attachments list as a header.
* src/widgets/modest-msg-edit-window.h:
        * Added support for exposing rich text editing format.
* Added src/widgets/modest-attachment-view.[ch]:
        * Widget showing an only attachment, with its size and icon. It's a refactoring
          of previous attachments view, splitting in specific widgets each attachment.
* src/widgets/modest-attachments-view.[ch]: big rework of this widget.
        * Now the "activated" signal passes a TnyMimePart instead of an attachmetn index.
        * Now it's a GtkVBox with the attachments one per line. They include the new
          ModestAttachmentView for showing each mime part.
* src/widgets/modest-msg-edit-window-ui.h:
        * Added support for rich editing actions.
* src/widgets/Makefile.am:
        * Added compilation of new ModestAttachmentView widget.
* src/widgets/modest-msg-view.[ch]:
        * Now attachments signal returns a TnyMimePart instead of an index.
        * Now attachments are shown as a header, using the new modest_header_view_add_custom_header
          method.
* src/modest-tny-msg.[ch]:
        * Support for sending html-formatted mails.
* src/modest-mail-operations.[ch]:
        * Now ..._send_new_mail gets both plain text and html versions of the message,
          to allow sending rich text messages.
* src/modest-runtime.c:
        * Add bullet list icons.
* src/modest-main.c:
        * Use the new _send_new_mail api supporting rich text messages (sends a NULL html
          field, as the command line API is only supporting plain text sends).
* src/modest-ui-actions.[ch]:
        * Update on_msg_attachment_clicked, as now it gets a TnyMimePart
          instead of an index.
        * (modest_ui_actions_on_send): updated to handle rich text messages
          (those with html and raw text versions).
        * Methods for rich text editor actions: ..._on_toggle_bold,
          ..._on_toggle_italics, ..._on_toggle_bullets, ..._on_change_justify,
          ..._on_select_editor_color, ..._on_select_editor_background_color,
          ..._on_insert_image.

pmo-trunk-r1469