Merge 'pri_key_refactor' into 'trunk'

r8497@Thesaurus (orig r8484):  ribasushi | 2010-01-31 10:06:29 +0100
Branch to unify mandatory PK handling
r8498@Thesaurus (orig r8485):  ribasushi | 2010-01-31 10:20:36 +0100
This is not really used for anything (same code in DBI)
r8499@Thesaurus (orig r8486):  ribasushi | 2010-01-31 10:25:55 +0100
Helper primary_columns wrapper to throw if a PK is not defined
r8500@Thesaurus (orig r8487):  ribasushi | 2010-01-31 11:07:25 +0100
Stupid errors
r8501@Thesaurus (orig r8488):  ribasushi | 2010-01-31 12:18:57 +0100
Saner handling of nonexistent/partial conditions
r8762@Thesaurus (orig r8749):  ribasushi | 2010-02-19 10:07:40 +0100
trap unresolvable conditions due to incomplete relationship specification
r8764@Thesaurus (orig r8751):  ribasushi | 2010-02-19 10:11:09 +0100
Changes