- 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 r278338, r278340, r278458, r278519:

Create a module to install the Raspberry Pi dtb files.

Pull in the rpi.dts -> rpi.dtb module (dtb/rpi) and have it install
rpi.dtb in /boot/dtb by default.

Add a module to build the dtb files for all supported imx6 systems.

Remove imx6s-wandboard.dts, there is no such file.

Add a "module" to build the dtb files for all supported imx6 systems.