Allow COPY's 'text' format to output a header

When Who What
2018-10-02 05:07:04 Michael Paquier (michael-kun) Closed in commitfest 2018-09 with status: Returned with feedback
2018-08-17 04:40:10 Michael Paquier (michael-kun) New status: Waiting on Author
2018-08-13 21:36:24 Andrew Dunstan (adunstan) Added adunstan as committer
2018-08-10 21:39:27 Andrew Dunstan (adunstan) Closed in commitfest 2018-07 with status: Moved to next CF
2018-07-26 16:45:17 Cynthia Shang (cshang) New status: Ready for Committer
2018-07-26 16:06:35 Simon Muller (samuller) New status: Needs review
2018-07-25 17:24:27 Cynthia Shang (cshang) New status: Waiting on Author
2018-07-24 15:11:34 Cynthia Shang (cshang) Added cshang as reviewer
2018-05-13 23:23:27 Simon Muller (samuller) Changed authors to Simon Muller (samuller)
2018-05-13 23:22:31 Simon Muller (samuller) Attached mail thread CAF1-J-0PtCWMeLtswwGV2M70U26n4g33gpe1rcKQqe6wVQDrFA@mail.gmail.com
2018-05-13 23:22:31 Simon Muller (samuller) Created patch record