Go slog 2.1

- Upped version to 2.1 because, why not?
- Added domain tag and value to log items
- Added blog name tag to log items
- Searching can now be done on the following columns:
	- domain
	- code
	- message
	- class
	- function
- Tweaked searching interface a bunch
- Added limit param when displaying log items
- Default interval is now 1 hour instead last 30 seconds
- Adjusted column widths so the results look a bit more balanced
- Data that was only being stored as a tag is now being stored in the JSON item
	- We were relying on the tags always being in the same spot in the array returned by Loggly and it turns out you can't rely on that
- Deprecated go_slog filter
	- Replaced with go_slog action
- Updated plugin description so it mentions loggly now instead of simple db
- Few other minor tweaks

https://github.com/GigaOM/gigaom/issues/5314
https://github.com/GigaOM/gigaom/issues/5310