TinyOWS - Generate id (with expose_pk) even if no PK is available

[colivier]

For instance to work with view or table with no PK

Report by Jukka:

Well, Geoserver is generating some random fid in that case, like 
<gml:featureMember>
   <topp:Vakken fid="fid-20a01e80_11c2d38a583_37bc">

I could not find easily how the Geoserver fid generator works. Anyway I
do not believe those fids are stable enough for deletes or updates.
However, they are usable for some strict WFS clients which are checking
both the existence of fid and that they are unique in the result set.
With missing fids or double fids they can refure parsing the result set.

I can see that Geoserver folks were considering to utilise oids with
PostGIS backend but I suppose that solution is not usable any more
because oids are not compulsory.
http://jira.codehaus.org/browse/GEOS-186

This is one more pecularity with the OpenStreetMap data, osm_id is not
necessarily unique but I must create a new serial column for PK. 
Right thing to do is naturally to have a primary key in tables.