EXAMPLE.awlpro: Add LIBS section

Signed-off-by: Michael Buesch <m@bues.ch>
project: Add support for library selections

Signed-off-by: Michael Buesch <m@bues.ch>
libsel: Also return string for unknown types

Signed-off-by: Michael Buesch <m@bues.ch>
gui: Write lib selections to project file

Signed-off-by: Michael Buesch <m@bues.ch>