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.

After testing a Python module, the build was broken because the test
created a __pycache__ dir, which CMake tried to install as a file because:

a) `if(IS_DIRECTORY foo)` requires a full path to work

b) For CMake, `IS_DIRECTORY(foo)` is not the same as `IS_DIRECTORY foo`

c) CMake is a pain sometimes

do not require building through a CMakeLists.txt.