Better configuration of JDBC connection pools

This PR is changing a way in which JDBC connection pool is configured. It exploits the fact that dataSources are JavaBeans-compatible so it's easy to set them up using property editors using available properties values. This approach is better from previous because:

* there is no need to take care of each setting individually (less boring coding),
* default values are correctly preserved for each implementation of connection pool (nothing gets set if no property is present)
* new settings of future versions of Tomcat connection pool / Commons DBCP, once available, will be automatically handled (true, they will be not tested, but it's still better)
* it's easy to add other implementation of connection pools in the future as long as they conform to JavaBeans spec.

Let me know what do you think.