Support for any OpenWrt 15.05.1 tch board

[LuKePicci]

Highlights:

• include tch/bcm gpl sources updated to 17.2.278
• new import script to bring in more tch/bcm gpl sources (kernel+sdk)
• patched buildroot to output binaries into subtarget specific folder
  • it's easy to merge binary package trees from different boards
  • userspace packages could be shared across same arch boards
• patched buildroot to select subtarget specific patches
• easy support for multiple kernels to be merged whenever we get it
  • kernel package reverted to vanilla linux version
  • bcm patches exported into subtarget patch
• fixed bcmdrivers impl symlinking
• arm arch is now correct, kmods load fine, vermagic matches
• some general cleanup

[LuKePicci]

Side notes:

• strongswan built fine from this tree
• I still can't keep kmod-tun alive with no panics on vbnto after creating the interface, may be my stripped kconfig does not match the real kernel enough yet
• roleo's Kconfig for vbntk from should provide more stable results, if you would like to add configs for vbntj take it as example