- Copy stable/10@296371 to releng/10.3 in preparation for 10.3-RC1
builds.
- Update newvers.sh to reflect RC1.
- Update __FreeBSD_version to reflect 10.3.
- Update default pkg(8) configuration to use the quarterly branch.

Approved by: re (implicit)

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