Idea: Use extended blocklist format to support installing to raid device.

[Bean]

Hi,

Currently, the blocklist format can only support traditional disk. I'm
thinking about a new format that can be used in raid as well.

The new format is like this:

checksum_0 blocklist_0 checksum_1 blocklist_1 ...

The checksum is the checksum of sectors in the blocklist that follows.
For example:

c1 10+20,40+10 c2 10+50

This means 10-30,40-50 sectors from one disk, then 10-60 sectors from
another disk. The checksum is used to find the correct disk.

For traditional disk, we can also use this format, for example:

c1 10+20,40+10

This can support install to different disk than the one core.img is
in, as it will scan all disks for the correct checksum at runtime.

-- 
Bean