ar71xx: Add Gainstrong MiniBox v1.0 support to trunk

ar71xx: Add Gainstrong MiniBox v1.0 support to trunk

This patch supersedes the v1 from September 17th.

Bumping the patch version - the MiniBox profile showed up under M, but
since it's called 'Gainstrong MiniBox v1.0' now it looks out of place.
Renamed the profile to gs-minibox-v1.mk to fix that.

The following patch adds support for the Gainstrong MiniBox into trunk
(or 'Designated Driver' :D ).

Fixed items:

- Inverted LED polarity (OOLITE seems to suffer from the same problem).
- Changed uppercase MINIBOX_V1_ prefix as requested.
- Prefixes are now gs_minibox_ similar to gs_oolite_ (same vendor).
- Mention the vendor (Gainstrong) in code headers.

Compiles fine, has been confirmed working by owners on 15.05.

Question: I've seen some boards use tools/firmware-utils/src/mktplinkfw.c,
the MiniBox images build fine without, so I'm wondering: do I need to add
it in there as well? Any added benefit?

Thank you

Signed-off by: Stijn Segers <francesco.borromini@inventati.org>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@47234 3c298f89-4303-0410-b956-a3cf2f4a3e73