Enables use of either GConf or GSettings as a configuration backend.

Should make translation easier.

Taking advantage of the new units in the last commit, I've moved some of the pages into their appropriate units.

Sidebar refactoring.  Large commit, to be sure, but this should make it much easier to manage the sidebar going into the future as well as put the intelligence for managing each branch in a separate compartment, where it belongs.  Other minor bugs were discovered while testing the code, fixed as well.

This fixes #3321 by altering the way we set the initial value of the radio action group, as well as making sure that the events directory page gets constructed with the proper sort setting (by making it read from the config).

Improves messages displayed when view collections are empty or when no items in the collection match the search filter. Closes #3213.

#3188: Find button added to toolbars on pages that show media (but not pages that show events).  Some other code cleanup too, including moving to a single Gtk.ActionGroup for common actions, meaning that LibraryWindow doesn't have to synchronize actions when pages are switched from (and that pages can monitor those actions for their own state, which cleans up EventDirectoryPage a bit).

#2229: Event name is now a date range for events spanning multiple days.  #2599: If an event is named, the date (or date range) appears in its tooltip along with its name.  Both courtesy Wolfgang Steitz.

#1110: Send pictures via Nautilus Send To integration.  #2248: Added View Event for Photo to the full-window page context menu.  #2735: Better temporary file management.  Now using /tmp and relying on the system to manage the files (i.e. delete them at boot time).  This change affects all users of temp files, the largest of which right now are the WebConnectors and Send To.

Cade changes in preparation for 0.11 (but these do not require 0.11 to compile).  0.11 features better code analysis, which is what it's warning about here.

#1560: Switched to using Gtk.Actions entirely in our Page code.  I've also restructured how Actions are registered with the UI Manager to deal better with multi-tiered class heirarchies (with MediaPage, we now have three-deep Page classes with Actions that must be registered).  I've also made it easier to update the Actions when ViewCollection state changes and pushed more common Action code (i.e. Undo/Redo) into LibraryWindow.

Introduces the new MediaPage class that treats photos and videos uniformly. As a consequence, allows editing titles and setting ratings for videos. Closes #2584.

Fixed regression in DataSource's signal reflection to DataView.  This fixes #2598, #2597, and #2595.Also updated strings for #2591 and #2610.

DataObjects no longer have an "altered" signal.  All "altered" signals come off their SourceCollection, which means it's easier to aggregate and issue them in a single signal.

#2422: Patch to make Shotwell more responsive while marking photos offline/online, as well as do the operation quicker than before.

Further optimizations in startup time.  Almost all pages (the Photos page is the lone hold-out) are stubs, the pages themselves created as they're accessed.  This has big wins on startup time.

#2302: On startup, now checking all photos at startup for online/offline status, including those outside the library directory.  This patch also includes various optimizations in linking/unlinking and freezing/thawing DataCollections, which improves the performance of marking online/offline status as well as moving to the trash.