remove order by downloads_id on missing downloads query to improve query performance
added media_edits.media_id column to reference media items that were edited
don't reference media.media_id from media_edits.media_id initially because media.media_id = 0 might not exist
"activities" schema and SQL migration file (copying edits from "media_edits" and "story_edits" into a new table)

Conflicts:
	script/mediawords.sql
	sql_migrations/mediawords-4421-4422.sql
media and story changes now logged to "activities" table

Conflicts:
	lib/MediaWords/Controller/Admin/Media.pm
order JSON keys alphabetically, just like Perl's JSON module does

Conflicts:
	sql_migrations/mediawords-4421-4422.sql
object_id is BIGINT (because it might refer huge tables)
"cm_story_merge" activity
"cm_media_merge" activity
"cm_remove_story_from_controversy" activity (both when a single story and multiple stories are being removed)
moved story removal SQL to a helper subroutine in model
"cm_mine_controversy" activity
"cm_dump_controversy" activity
"cm_search_tag_run" activity
"cm_search_tag_change" activity
removed 'language="javascript"' attribute in <script> because it's obsolete
missing closing tag in <link />
"boxtitle" is better off as a CSS class and not ID because it is not unique in a HTML page
"even" is better off as a CSS class and not ID because it is not unique in a HTML page
closing <td> tag