access: fix PostgreSQL compatibility
- Fixes sql queries to improve standard compliance and compatibility: "RLIKE", quoting. (addresses #3214)
- Fixes problem of assignement of -1 to a foreign key, removing foreign key and shaping relationship to exclude -1 value. (closes #3099)
- PEP8/257 code style improvements.
Signed-off-by: Leonardo Rossi <leonardo.r@cern.ch>