- Copy stable/10@285827 to releng/10.2 in preparation for 10.2-RC1
builds.
- Update newvers.sh to reflect RC1.
- Update __FreeBSD_version to reflect 10.2.
- Update default pkg(8) configuration to use the quarterly branch.[1]

Discussed with: re, portmgr [1]
Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

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)

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

Requested by: secteam (cperciva, des)
Approved by: bapt

Add infrastructure for installing pkg(8) keys into /etc/keys/pkg and add
the current test key that packages will be signed with until 10.0-RELEASE.

Approved by: bapt
Discussed by: bapt with des
MFC after: 2 days