* Added src/widgets/modest-recpt-view.[ch].

* Added src/widgets/modest-recpt-view.[ch].
        * Inherits from GtkLabel.
        * It's a tweaked GtkLabel for showing a list of recipients.
        * Main feature is the way it handles selections (tries to
          select a full recipient).
        * Emits a signal when a recipient is selected and clicked/
          double clicked.
* Added src/widgets/modest-mail-header-view.[ch].
        * Contains implementation of ModestMailHeaderView, which is
          an implementation of TnyHeaderView.
        * It's used in ModestMsgView to show the mail headers.
        * It shows the recipients list with the new ModestRecptView
        * It features an expansor, to hide or show more headers.
* src/modest-text-utils.[ch]:
        * Added modest_text_utils_split_addresses_list. It splits a
          list of email addresses in the format accepted by mail
          recipients list.
* src/modest-ui-actions.[ch]:
        * Added stub handler for message recipient activation (click on
          emails in a mail header).
* src/gtk/modest_main_window.c:
        * Main window GtkVBox spacing is now 0 for better HIG compliance.
        * Now scrolled windows are added with shadow (HIG compliance).
        * Added handling of signal from recipients in mail preview.

pmo-trunk-r868