Set Up InitializationFilter.java for PostgreSQL

Add required support for initialization like setting drivers, database specific queries in initialization filter for PostgreSQL. For example setting up drivers See here :

https://github.com/openmrs/openmrs-core/blob/9df11cbb03d84f0b0578c4356f40d1cb2c1643c3/web/src/main/java/org/openmrs/web/filter/initialization/InitializationFilter.java#L1152