makeconf: change the channel input loop to a one-liner

The "would you like to add a channel?" ... "would you like to add
another channel?" loop is very verbose and slow to use. This proposal
makes it a simple one-liner where the user can enter a bunch of chans
using any combination of space/comma/semi-colon as a separator, or
just hit enter to proceed without channels...
makeconf: offer freenode by default
makeconf: revise the output and reduce the noise

Long "would you like ZNC to..." questions are slow to read.
Use short and pithy prompts, and try to fit the line width to
less than 80 characters. Furthermore, Remove Word Capitalization.