Fixes and add-ons for b-tagging and trigger workflows

- Added an option of switching the b-tagging selection into tagging mode (modified a2cbbf2bd). This is useful for measuring the b-tagging efficiency as well as the trigger workflow as it improves statistics.
- Fixed the bug in the Z selection for tag and probe studies. Now (tag==probe) won't happen anymore.
- Storing full four-vectors of trigger objects, rather than just pt/eta/phi.