Comprehensive re-write of the classicupgrade HowTo and other changes

[Marc Muehlfeld]

Hello,

I re-wrote the parts in the HowTo, saying that the group migration for
tdbsam and smbpasswd backends don't work. I've added a list of databases
that have to be copied to 'dbdir', that is used by the classicupgrade.
I've added all *.tdb files, I found out. If you know more (and their
default location), please let me know. I'll add them.

https://wiki.samba.org/index.php/Samba_Classic_Upgrade_%28NT4-style_domain_to_AD%29


Regards,
Marc