safe-upgrade bootstrap force not upgrading "ART" partition name into lowercase "art"

[javierbrk]

When upgrading from older versions of libremesh without safe-upgrade in librerouter v1, ART partition remains in UPERCASE and the kernel does not recognize that partition. So safe-upgrade should take current boot command line and change the ART partition name to lowercase. Also it can be usefull to have a script that boostraps the router when instaling the package to fix this automatically without manual intervention