LUTECE-1825 : fix init,upgrade script for postgres

Use ' as a string literal delimiter (and '' to escape ')
Add a substition for PostreSQL so that backslash escaping is
correctly interpreted.
An incorrect value is still injected for Oracle.
LUTECE-1827 : Add Bean to inject a SitePropertiesGroup customizable into context file
Merge pull request #2 from rzara/LUTECE-1825

LUTECE-1825 : fix init,upgrade script for postgres