Do not use local mke2fs feature configuration to determine flags for ext fs

It could have features not desirable or supported in target system;
hardcoding them is a bit more robust.
Do not fail if firewall-offline-cmd is not present

This returns attempt at lokkit for firewall configuration and ignores
failure as used to be the case with lokkit.
Add support for creating and mounting FAT filesystems
Add possibility to set up a loopback device with size and offset

Useful for partitions. Also, we can't touch the underlying storage then,
treating the loopback volume as a physical disk partition.
Add partitioned disk creator
Make is possible to create a multi-partition image with MBR table
Install GRUB bootloader