Merge lp://staging/~sinzui/bzr-gtk/ui-factory into lp://staging/bzr-gtk

Add GtkUIFactory implementations and missing tests.

This branch was extracted from my effort to guarantee that the progress bar
shows when I use gpush.

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RULES

    * Add tests for all the implemented classes and specifically GtkUIFactory.
    * Add ._progress_updated() and .report_transport_activity() that are
      needed to update the progress widget.
    * Add the message, warning, and error dialogs.
      * Maybe update the Confirmation dialog to extend MessageDialog?
    * ADDENDUM: Let me run just one test module!

LINT

    added:
      tests/test_ui.py
    modified:
      setup.py
      tests/__init__.py
      ui.py

TEST

    ./setup.py check
    or
    ./setup.py check -m test_ui

IMPLEMENTATION

I was frustrated running the whole suite which takes 18 seconds on my
computer. I updated the test runner code to use existing 'discover'
option to run the whole suite, or accept a single module as an arg. The
ui tests complete in 0.107s on my computer.
    setup.py
    tests/__init__.py

I First added tests for the existing classes. I have never used this
many mocks in a test suite before, they definitely make the tests fast,
though I thought I might have used too many. I tried removing a few but
the tests could become may times slower or just never complete without
forcing the Gtk.main_loop to run.
    tests/test_ui.py

I then added test for new methods and refactored some of the code.
* I extracted the main_iteration code in one method to a decorator
  function that I used on several progress bar methods to ensure
  the UI updates immediately.
* I added the Info, Warning, and Error dialogs and refactored PromptDialog
  to extend Gtk.MessageDialog. This provides an icon with the text
  message, as well a guarantees that the spacing and layout conforms
  to Gnome HIG.
* After I extracted the main_loop iteration rules from update(), changed
  self.fraction to fraction because nothing used it. I changed the error
  to a ValueError because it can only be caused by insane inputs.
* I extracted the common progress window and panel methods to
  ProgressContainerMixin which was easy since I had already written
  tests to that used a similar mixin to verify their function.
* I updated ProgressPanel to GtkBox since GtkHBox is deprecated.
* I added show_user_warning, which is almost identical to the TextUI
  implementation.
* I added ._progress_updated() and .report_transport_activity() which made
  the gpush progress bar show sooner and update more often.
    ui.py
    tests/test_ui.py