Raise CMake requirement to 3.0+

FindPythonLibs.cmake from CMake 2.8.x is not capable of finding Python
libraries on Maui, updating to CMake 3.x solves the problem.

Looks like it is better crafted.

Other parties interested in Calamares should already have CMake 3.x
so this is not a problem.
Fix autologin in displaymanager module
Improve diacritics transliteration.
Compare with None
Replace unsquashfs with unpackfs

Conflicts:
	src/modules/unsquashfs/unsquashfs.conf
Check for fs name validity.
List all files recursively.
Revert "Raise CMake requirement to 3.0+"

This doesn't work when the partition manager is enabled because it
uses ECM and ECMConfig.cmake fails with an error if the required
CMake is not less than 2.8.13

Added a note here to remember about this.

This reverts commit 2020eb0eb306f7319b2376b06acb8e242e7b7dc3.