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.
This reduces chances of errors where consumers of strings mutate inputs
and reduces memory usage of the app.
Test suite passes now, but there may be some stuff left, so we will run
a few sites on a branch prior to merging
