Eventlog updates (#9633)

* Eventlog updates
remove host from eventlog table, retain in api
allow most fields nullable

* updated schema

* revert auth for legacy log_event function
safer check in the model

* add function modifiers

sql-schema/280.sql

@@ -0,0 +1,5 @@
+alter table eventlog modify device_id int unsigned null;
+alter table eventlog modify reference varchar(64) null;
+alter table eventlog modify severity tinyint default 2 not null;
+drop index host on eventlog;
+alter table eventlog drop column host;