Create a method to disable triggers

Currently, there is no easy way to temporarily disable triggers. This is important for some users. It might be a good idea to have some (maybe not all?) of the following:

Temporarily disable all triggers on a particular table:

ALTER TABLE foo DISABLE TRIGGERS;

Re-enable the triggers:

ALTER TABLE foo ENABLE TRIGGERS;

Disable a particular trigger on a table:

ALTER TABLE foo DISABLE TRIGGER bar;

Re-enable it:

ALTER TABLE foo ENABLE TRIGGER bar;

Disable triggers for a particular user:

ALTER TABLE foo DISABLE TRIGGERS FOR CURRENT_USER();

Disable all triggers for current session (maybe requires superuser privileges?):

SET disable_triggers = ON;