Merge branch 'base-image-only-build'

Adds an option to build with none of the packages marked with "=m" by setting BASE_IMAGE_ONLY to "Yes"
add an option to not build any packages that are not in the image ( replaces =m with =n )
Update build.sh
Merge https://github.com/noblepepper/openwrt-yun into base-image-only-build

Conflicts:
	build.sh
Merge pull request #14 from noblepepper/base-image-only-build

add an option to not build any packages that are not in the image