fstab.conf: Add a new "crypttabOptions" option that defaults to "luks".
            Document that for Debian and Debian-based distributions, the
            setting should be changed to "luks,keyscript=/bin/cat".

main.py: Append the options from the above setting to the end of every
         line in crypttab.

At least the "luks" option should always be there, because there may be
different encryption types. The Debian initramfs-tools also require the
Debian-specific keyscript option and will otherwise ignore the keyfile
entirely (see pull request #254).

At least the Debian update-initramfs needs the entry to be there (see
pull request #254). Dracut will probably need it too. And logically, it
should be there.

i.e. not just required by the netinstall module.

The netinstall module requires Qt >= 5.6 instead of
Qt >= 5.3

These job plugins work similarly to view modules, with the following
differences:

* These jobs need to link only libcalamares, not libcalamaresui. For
  this reason, PluginFactory was moved from libcalamaresui to
  libcalamares. (It depends only on QtCore.)

* Instead of deriving from ViewModule, derive from CppJob (which is a
  subclass of Job).

* Like process and Python jobs, a job plugin is a single job, whereas a
  ViewModule can generate a whole list of jobs.

The CppJob and CppJobModule classes are new. In Module::fromDescriptor,
the combination type=job, intf=qtplugin is now supported and mapped to
CppJobModule.

locale -a returns the locales using ".utf8" names rather than ".UTF-8".
The case-insensitive match does not help because it is "utf8" rather
than "UTF-8". So we need to match both with and without the dash.

Revert "Merge upstream changes"

Merge upstream changes

Merge upstream changes

The arrow no longer changes direction depending on whether
the button is clicked or not.

The button is "not checked" by default, and becomes
checked when clicked; the packageview becomes visible
when the button is checked.

Merge upstream changes