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.
This also adds ImageRegistry, a SVG cache, a bunch of utility functions
for shared pixmaps in CalamaresUtilsGui and renames several qrc files
in viewmodules.
Now linking with -Wl,--no-undefined!
Moved find_package KF5 from the root CMakeLists.txt to the partitioning
module where it belongs. KF5 deps should be limited to plugins.
Lots of random fixage to make stuff link.
Removed CalamaresApplication reference from Settings.
Removed the use of AbstractPage, we don't need it right now.
