More sanity checks when the server starts

[Alan DeKok]

  I've pushed some more code which sanity checks the dynamically
expanded configuration items.  e.g. for the "detail" module, you can do:

	filename = ${radacctdir}/%{%{Packet-Src-IP-Address}:- ...

  In v3.0.4 and earlier, typos in the "filename" would result in
run-time errors.  Which are hard to debug. :(  For future versions,
these typos are caught when the server loads:

./raddb/mods-enabled/detail[34]: Failed parsing expanded string:
./raddb/mods-enabled/detail[34]:
/usr/local/var/log/radius/radacct/%{%{Picker-Src-IP-Address}:-%{Packet-Src-IPv6-Address}}/detai...
./raddb/mods-enabled/detail[34]:                                       ^
Unknown attribute

  This is much friendlier to administrators.  It doesn't cause any
issues, and it means that typos are caught quickly.

  As a result of this change, I've fixed a few typos in the SQL queries.

  Alan DeKok.