Statement-level history tracking

[wesleykendall]

I'm considering support for conditional statement-level triggers in pgtrigger. While this isn't a native feature of Postgres triggers, there are ways to still support it.

If supported, this would allow pghistory triggers to be statement-level, meaning there would be one bulk history event insertion instead of N happening for each row in a bulk insert or create. This could be a substantial performance boost for those tracking history across bulk inserts/upserts/deletes.

Let me know what you think. I'm aiming to incorporate this without breaking the main interface. Just toggle a flag in pghistory.track or a setting, and all triggers will be migrated to statement-level triggers

[wesleykendall]

This was implemented in #197 and released in version 3.6.0