The INSTALL_CONFIG is "on" by default. When set to off,
no *.conf file, both global and related to a single module,
will be installed. A warning message is printed by cmake too,
and the module description is edited to make this visible.
This is useful for testing, when we want to install our
own libraries and binary but keep the configuration of the
live system we are testing on (e.g. path to distro image).
Tested on the master branch.
This also adds ImageRegistry, a SVG cache, a bunch of utility functions
for shared pixmaps in CalamaresUtilsGui and renames several qrc files
in viewmodules.
Module descriptors are now module.desc, no configuration allowed inside.
Module config files are <modulename>.conf, installed in
share/calamares/modules.
settings.conf is read from /etc/calamares, then share/calamares, and if
running with --debug also in the current dir.
Module config files are read from /etc/calamares/modules, then
share/calamares/modules, and if running with --debug also in
src/modules/<modulename> relative to the current dir.
