move target/default/target_skeleton into package/base-files, put all the default files in ipkg packages, cleanup some junk in toolchain/, toolchain/ no longer changes build_mipsel/root


git-svn-id: svn://svn.openwrt.org/openwrt/trunk/openwrt@1494 3c298f89-4303-0410-b956-a3cf2f4a3e73