Update DbConnection.py

QGIS 2 modification
Update metadata.txt

QGIS 2 modification
Update postgis.py

QGIS 2 modification
Update spatialite.py

QGIS 2 modification
Update __init__.py

QGIS 2 modification
Update spatialite.py

QGIS 2 modification
Update readme
Update postgislayer.py
Merge pull request #5 from Ronald-Mulder/master

QGIS 2 adaptation