Further work to figure out the best way to handle params with data-in-modules.

This work focuses on returning the lookup() calls to init.pp by renaming
all the private hiera variables to ntp::defaults::x as a proposed
standard.

Other options considered:

ntp_default::x
default_ntp::x
ntp_x
default_x
defaults = {'x' => 'thing'} and then doing lookup(defaults[x]).