UI improvements, support requests, MD5Sum, Windows hidden directories & fixes

This is for testing purpose only.
Do not install it, unless you know what you're doing.

Improvements for all users:

• You can now request support directly from the application.
• On the onboarding screen, you'll be warned in case you typed your email
  address instead of the address of your Cozy.
• The app will now start by default on login. You can still disable it in the
  settings.
• The activity indicator is now visible on deletions.
• Links are now opened in a new windows, so users don't end up with no way to
  get back.
• The content of a folder renamed offline will not be uploaded again.
• When a file was both updated locally and trashed remotely, it will be kept
  with the updated content.
• The app now enforces MD5Sum for all files, to ensure data consistency and to
  prevent weird issues.
• Disk space and revocation error messages should be clearer.
• Logs are easier to filter, which should help us to debug synchronization
  issues.

Improvements for Windows users:

• You should not see weird .cozy-desktop directories anymore (including in
  your home and your Cozy Drive directories).
• Fixed an issue with last modification date, which was preventing a file first
  uploaded through the Cozy Drive web app, then renamed locally, to be synced.