MDL-43557 events: removed underscores from event string keys

AMOS START
 MOV [event_legacy_logged, logstore_legacy],[eventlegacylogged,logstore_legacy]
 MOV [event_cohort_created,cohort],[eventcohortcreated,cohort]
 MOV [event_cohort_deleted,cohort],[eventcohortdeleted,cohort]
 MOV [event_cohort_member_added,cohort],[eventcohortmemberadded,cohort]
 MOV [event_cohort_member_removed,cohort],[eventcohortmemberremoved,cohort]
 MOV [event_cohort_updated,cohort],[eventcohortupdated,cohort]
 MOV [event_group_created,group],[eventgroupcreated,group]
 MOV [event_group_deleted,group],[eventgroupdeleted,group]
 MOV [event_group_member_added,group],[eventgroupmemberadded,group]
 MOV [event_group_member_removed,group],[eventgroupmemberremoved,group]
 MOV [event_group_updated,group],[eventgroupupdated,group]
 MOV [event_grouping_created,group],[eventgroupingcreated,group]
 MOV [event_grouping_deleted,group],[eventgroupingdeleted,group]
 MOV [event_grouping_updated,group],[eventgroupingupdated,group]
 MOV [event_webservice_function_called,webservice],[eventwebservicefunctioncalled,webservice]
 MOV [event_webservice_login_failed,webservice],[eventwebserviceloginfailed,webservice]
 MOV [event_webservice_service_created,webservice],[eventwebserviceservicecreated,webservice]
 MOV [event_webservice_service_deleted,webservice],[eventwebserviceservicedeleted,webservice]
 MOV [event_webservice_service_updated,webservice],[eventwebserviceserviceupdated,webservice]
 MOV [event_webservice_service_user_added,webservice],[eventwebserviceserviceuseradded,webservice]
 MOV [event_webservice_service_user_removed,webservice],[eventwebserviceserviceuserremoved,webservice]
 MOV [event_webservice_token_created,webservice],[eventwebservicetokencreated,webservice]
 MOV [event_webservice_token_sent,webservice],[eventwebservicetokensent,webservice]
 MOV [event_user_loggedin,auth],[eventuserloggedin,auth]
 MOV [event_assessable_uploaded,assignsubmission_file],[eventassessableuploaded,assignsubmission_file]
 MOV [event_assessable_uploaded,assignsubmission_onlinetext],[eventassessableuploaded,assignsubmission_onlinetext]
 MOV [event_chapter_created,mod_book],[eventchaptercreated,mod_book]
 MOV [event_chapter_deleted,mod_book],[eventchapterdeleted,mod_book]
 MOV [event_chapter_updated,mod_book],[eventchapterupdated,mod_book]
 MOV [event_chapter_viewed,mod_book],[eventchapterviewed,mod_book]
 MOV [event_book_exported,booktool_exportimscp],[eventbookexported,booktool_exportimscp]
 MOV [event_book_printed,booktool_print],[eventbookprinted,booktool_print]
 MOV [event_chapter_printed,booktool_print],[eventchapterprinted,booktool_print]
 MOV [event_message_sent,mod_chat],[eventmessagesent,mod_chat]
 MOV [event_sessions_viewed,mod_chat],[eventsessionsviewed,mod_chat]
 MOV [event_answer_created,mod_choice],[eventanswercreated,mod_choice]
 MOV [event_answer_updated,mod_choice],[eventanswerupdated,mod_choice]
 MOV [event_report_viewed,mod_choice],[eventreportviewed,mod_choice]
 MOV [event_assessable_uploaded,mod_forum],[eventassessableuploaded,mod_forum]
 MOV [event_assessable_uploaded,mod_workshop],[eventassessableuploaded,mod_workshop]
AMOS END
MDL-43557 events: renamed event class names

1) The core 'item_tagged' class was renamed to 'tag_added'.
2) The core 'item_untagged' class was renamed to 'tag_removed'.
3) The core 'message_read' class was renamed to 'message_viewed'.
4) The mod_forum 'userreport_viewed' class was renamed to 'user_report_viewed'.
5) The report_outline 'activity_viewed' was renamed to 'activity_report_viewed'.
6) The report_outline 'outline_viewed' was renamed to 'report_viewed'.
MDL-43557 mod_lesson: removed incorrect usage of snapshots
MDL-43557 events: fixed minor issues in existing events
Changed notes_viewed event description
Re-added the 'relateduserid' other field when triggering the course_module_completion_updated event
Changed the descriptions for the mod_assign submission_created and submission_updated event
Added description to the \mod_quiz\event\attempt_deleted event
Fixed 'other' docs for events