This is a small note to describe the different security levels, specifically
when using the "import_file" command.  There are currently 6 different security
levels available:

    --minimal-security
    --very-low-security
    --low-security
    --medium-security
    --high-security
    --extreme-security

I have to say up front that I don't know for sure if these actually provide any
real difference in security.  It is my theory that it would be easier for a 
cracker to reassemble a file stored in minimal-security mode than one in the
extreme-security mode, but I have no proof of this.  It is only my theory.

These levels simply control how spread out the file is when it is stored on
the disk.

The --minimal-security mode is for files that really don't have any really 
private information in them at all.  They are the fastest files to read and 
write because they are stored on disk almost contiguously.

The --very-low-security, --low-security, --medium-security, and --high-security
modes each spread the file out more on the disk.  The idea being that it is 
more difficult to piece it back together when it is scattered out more on in
storage.

The --extreme-security mode places each block in a completely random location
in storage, making it extremely slow to read and write.  I don't recommend
storing any really large files in this mode, it could take an hour to write
or read it.

