remove jsoncheck's check_format()

blueprint modularize-doctest

The split between process_file (formerly main) and check_format resulted
in a function signature that had three parameters transport four pieces
of information (path indicated whether formatting should take place). The
function used an exception to return a custom warning message when JSON
files were not properly formatted.

This patch merges these two functions and splits out format_parsed_json
instead, which takes one argument and returns formatted JSON. This also
eliminates the FormattingException.

Change-Id: Ia15e862abe181909e4007817c97ceb6ce9e133e7