New Cozy v3 design, Windows 7/8 favorite & various fixes

Hello there! Sorry for the summer delay, the team took some rest, and recently
we were quite busy working on some huge synchronization improvements, but
that's for another story. So let's get back to the current release...

Improvements for all users:

• The onboarding (the successive screens where you configure Cozy Drive for
  Desktop on first launch) now follows the new Cozy v3 design guidelines and
  wording. The other screens were mostly updated too, especially the settings
  which were merged into a single tab. In future releases, the tabs should
  move to the top and we should progressively transition to a new popover
  layout sticking to your systray, instead of the current floating window.
  Some screens will still make use of a separate windows when relevant
  (e.g. the Help one).
• We also enlarged the Cozy login screen, the authorization screen (were you
  allow the Cozy Drive for Desktop app to access the data in your Cozy) and
  the Dashboard screen (the one showing recent updates). In case your display
  has a small resolution, the app should not exceed the available space and
  fall back to scrolling.
• The disk space gauge should now effectively match the available space.
• The app was occasionnaly crashing on startup with a weird db Lock error.
  This should not happen anymore. Please shout out loud in case it still does
  for you.
• We fixed an issue that was preventing errors to be properly notified
  when sending a support request from the Help screen. We also made sure
  that a favorite creation failure would not block the application.
• We now have traces of failures for almost everything in the app except for
  upgrades (which unfortunately seemed to be the source of issues recently, so
  we'll probably add it too). This should help us fix issues regarding the
  onboarding step for example.
• We also added some missing translations.
• Last but not least we added the hopefully last missing checks to detect
  conflicts while trashing/deleting folders from the Cozy.

Improvements for Windows users:

• Once configured, the app now adds a favorite to Windows 7 and Windows 8.x
  explorer.
• While uploading files from a Windows device, missing folders creation was
  failing. This is fixed now.
• We changed the way we hide some special folders on Windows. We extensively
  checked it was working as usual on every supported Windows version, so this
  should not be visible in any way for you. But in case you still start seing
  some weird .cozy-desktop or .system-tmp-cozy-drive directories, please
  tell us.

Happy syncing!