Add gluon-legacy package with legacy upgrade scripts

package/gluon-config-mode/files/etc/config/gluon-config-mode

...luon/upgrade/config-mode/invariant/001-migrate-uci-config

package/gluon-core/files/etc/uci-defaults/zzz-gluon-upgrade

package/gluon-legacy/Makefile

...age/gluon-legacy/generate/lib/gluon/legacy/legacy-upgrade

...luon-legacy/generate/lib/gluon/legacy/legacy-upgrade-late

...b/gluon/upgrade/config-mode/legacy/010-migrate-configured

...gacy/generate/lib/gluon/upgrade/core/legacy/001-sysconfig

.../generate/lib/gluon/upgrade/core/legacy/011-gluon-network

...egacy/generate/lib/gluon/upgrade/core/legacy/020-wireless

.../lib/gluon/upgrade/lock-password/legacy/010-lock-password

...enerate/lib/gluon/upgrade/mesh-batman-adv/legacy/010-mesh

...luon/upgrade/mesh-vpn-fastd/legacy/010-reset-fastd-config

...enerate/lib/gluon/upgrade/simple-tc/legacy/010-migrate-tc

package/gluon-mesh-vpn-fastd/fastd.pl