Add simple examples of statement > newline parsing

Correct skipping is needed to correctly parse significant newlines
in input text.

Provide two examples of parsing statements separated by newlines.
In sn_parsing, demonstrate use of qi's blank_type to only skip proper
spaces and tabs. In sn_list_parsing, demonstrate use of skip
directive to allow continuation across newlines, in this case parsing
a list with each list element on a separate line.
Improve list continuation grammar

Allow lists to be spread arbitrarily across lines