Improve update-l2database.pl

* add & use adapted version of Net::SNMP::Mixin::Util::normalize_mac()
  (needed because one stray MAC was outputing as ASCII, untranslated)
* delete old copy of update-l2database.pl from sflow directory
* copy comment about testing status on switches from old sflow version,
  and add Extreme BD-8806 to list
* apply $do_nothing to *all* DB-affecting actions
* improve debug output layout and increase output
* replace a printf occurrence with print
* standardise whitespace
Add switch models to compat-comments in update-l2database.pl
Update foreign refs
Merge branch 'inex-live'
[BF] Force these to lower case to avoid confusion
[IM] Make it clearer what the CMS login form is about.
Merge pull request #47 from rowanthorpe/update-l2database-fixes

Improve update-l2database.pl
[IM] Added per @rowanthorpe

See #62
> I would just add that I found adding that 'urlbase' value to the config has proved very helpful
> for skinning (I've referenced it several times in doc pages especially), and I suggest that
> perhaps it is worth adding that to application.ini.dist anyway, irrespective of its use for cms
> login...?
Merge branch 'master' of https://github.com/inex/IXP-Manager