lib/colors: check for /etc/terminal-colors.d/[util].disable

[kzak@redhat.com: - move paths to pathnames.h,
                  - use static path buffer]

Signed-off-by: Ondrej Oprala <ooprala@redhat.com>
Signed-off-by: Karel Zak <kzak@redhat.com>
lib/colors: add info to man pages, add terminal-colors.d.5

Co-Author: Ondrej Oprala <ooprala@redhat.com>
Signed-off-by: Karel Zak <kzak@redhat.com>
lib/colors: support <name>.enable too

Signed-off-by: Karel Zak <kzak@redhat.com>