MFC r257344,r257403:

  Move /etc/keys to /usr/share/keys where users are less likely to modify them.

Approved by:	bapt
Approved by:	re (gjb)
MFC r257378,r257400,r257402,r257440:

  Add a pkg(7) manpage for bootstrap

Approved by:	bapt
Approved by:	re (gjb)