Find & Replace and Autotag watched words were not completely exported
and import did not work with these either. This commit changes the
input and output format to CSV, which allows for a secondary column.
This change is backwards compatible because a CSV file with only one
column has one value per line.
This commit includes other various improvements to watched words.
auto_silence_first_post_regex site setting was removed because it overlapped
with 'require approval' watched words.
Peter Wagenet
Bianca Nenciu
Robin Ward