Use read-write persistence when testing upgraded USB installations.

Otherwise e.g. the permission fixes won't get applied, and the
subsequent steps testing the permissions will fail.
Provide a source-destination mapping for persistent mounts.

Knowing that relationship makes it possible to do the permission
checks in the "persistent directories have safe access rights" step
without exceptions for each destination not in /home/$LIVE_USER.
Actually check that the ISO's Tails is installed.

The step "Tails is installed on USB drive $TARGET" only checks that
the *running* Tails is installed on $TARGET, which obviously fails
when doing an upgrade from ISO running an old Tails. That it worked
for the same scenario running the current Tails is just incidental.
Fix typo.
Unmount ISO when done with it.
Merge branch 'bugfix/7443-persistent-files-permission' into testing
Merge branch 'bugfix/7345-upgrade-from-iso-from-1.0-to-1.1' into testing
Merge branch 'testing' into devel
Merge branch 'devel' into experimental
Disable FoxyProxy's proxy:// protocol handler. (Closes: #7479)

FoxyProxy adds the proxy:// protocol handler, which can be used to
configure the proxy via an URI. A malicious webpage can include (or a
malicious exit node can inject) some JavaScript code to visit such an
URI and disable or otherwise change Iceweasel's proxy settings.

While using this to disable proxying will be dealt with safely by our
firewall, this could be used to defeat stream isolation, although the
use must be tricked into accepting the new proxy settings.
Merge remote-tracking branch 'origin/bugfix/7079-shared-mime-info-1.3' into testing
Revert "Bump pining value for wheezy-backports' shared-mime-info."

This reverts commit 63653ec627148d6512dc780486edb5b42ce7b435.

We have now removed shared-mime-info from our APT suite, and install a
newer one from Wheezy backports.
Merge branch 'testing' into devel
Merge branch 'testing' into experimental
Merge remote-tracking branch 'origin/feature/7479-disable-proxy-protocol-handler' into testing
Merge remote-tracking branch 'origin/testing' into testing
Merge branch 'testing' into devel
Merge branch 'devel' into experimental