[ewiki] new sample layouts, flat file db backend

There are a few new example-* layouts available (verbatim
copies from http://oswd.org/), but I'm wondering if they
should go in the main tarball or into the extra package.

#

After multiple requests for an enhanced flat file database
backend, there it is: "plugins/db/dzf2.php"
Unlike db/flat_files it stores filenames always in the same
fashion, regardless of OS, they are always compressed and
a few caching mechanisms will be added. It is case-insensitive
even on UNIX, and manages its files in subdirs for faster
access (when page versions grow). It is especially more quick
with "FIND" and "GETALL".
It is experimental, and no upgrade script will be provided
(that's a matter of ewikictl --backup --all and --insert).

#

All database_*() functions currently have a hack within the
"FIND" subfunction, which initially should help with the
<img> tag generation (for [internal://md5md5md5] links). I'm
not sure, but eventually "FIND" should concentrate on FINDing
again, and let the rendering/linking functions fetch the
{meta} field themselves with an additional GET?  This was
slightly slower for SQL, and no speed enhancement for
flat_file alikes - but only affected inline image linking.

Additionally there is yet no other part of ewiki using that
builtin {meta} retrieval of the "FIND" database subcall,
therefore it seems completely redundant now.

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