Initial implementation of support for stacked queries.

Added method to test for Time based blind SQL injection query stacking
on the affected parameter a SLEEP() or similar DBMS specific function.
Adapted libraries, plugins and XML with the above changes.
Minor layout adjustments.

lib/core/settings.py

@@ -64,3 +64,5 @@ PGSQL_ALIASES     = [ "postgresql", "postgres", "pgsql", "psql", "pg" ]
 ORACLE_ALIASES    = [ "oracle", "orcl", "ora", "or" ]
 
 SUPPORTED_DBMS    = MSSQL_ALIASES + MYSQL_ALIASES + PGSQL_ALIASES + ORACLE_ALIASES
+
+TIME_SECONDS      = 5