Results in better error messages.

A strange 'unknown' target has NULL fields otherwise.

MySQL has restriction for index size, so make the fields shorter.
100 should be enough for class and member names.
50 should be enough for domain name.

We'll delete these targets later, but for now I want to be able to
insert them.

I though Date.parse() returns a date, but it returns milliseconds
instead.

Picked an easily recognizable date - if needed we can replace this date
later with NULL or whatever else seems suitable.

Add conversion to change JavaScript booleans into 0 and 1 for MySQL.

For each user retrieve e-mail and determine if he's a moderator.

Removed the email_hash field from users table - a premature
optimization, we can calculate it on the fly which should be fast enough
as it's a simple md5, and it's only needed for displaying comments.

Rename read_comments table to readings.

Extract readings info from mongo_metas.

Some users have subscribed without having commented or voted.  This
added additional complexities as subscription db in mongo lists users by
external_id unlike all other tables which list the username... oh crap.

Refactored things around considerably.  Mongo comments and subscriptions
are now loaded up front, so all following procedures can operate on
them.  Added lots of messy logic into UsersTable, building an additional
index by external_id and looking up usernames from Sencha Forum db by
external_id. Thankfully it's a throw-away script, as the resulting code
is quite fragile and messy.

Also found one user who had subscribed bot no more has an entry in
Sencha Forum database.  Going to throw away his 3 subscriptions.

Plus include all voters to users table - some users have only logged in
to vote - for them the only trace we got is the username in upVotes or
downVotes array.

Generate ID-s for all tables and link users and targets from comments
table by ID-s.

Most comments have both author and userId field, but some earlier
comments lack the latter, so we query the sencha forum database to find
out the ID-s by username.

Also change users.name field to users.username - more clear.

A link to Sencha Forum database.

That field is not used in current comments database, having it
is also a premature optimization.

Because almost all queries need to exclude the deleted comments,
it helps having a view that excludes these.

Instead of two fields 'ext-js' and '4' we can have just 'ext-js-4'.
Simplifies most queries.

Gives much cleaner look to our methods list.  This is also the way how
other JavaScript documentation tools display the method signature.