Adds multiple description field support

maker.py: Adds stub function to grab descriptions in hopes
of later being able to add multiple description field support
to the interactive overlay creation session.

X-Gentoo-Bug: 465730
X-Gentoo-Bug-URL: https://bugs.gentoo.org/465730
maker.py: Adds Exception raising for errors
utils.py: Adds get_input() and get_ans() functions
maker.py: Migrates prints to self.output messages

Also cleans up large messages to tidy up the code and make it more
legible.
maker.py: Migrates to get_ans & get_input from utils.py