statement caching proof of concept

This is just proof of concept. More work has to be done to make it
build properly and work properly under different jdk's

Couple of questions.

1) What to do if there are multiple concurrent requests per
connection for the same statement?
1) we could just allow it
2) we could return a non-cacheable preparedstatement
3) throw an exception

2) Is it enough to cache prepared statements or should we cache
statements too?

Note: this work is based completely on apache's dbcp statement
caching implementation and this will be noted in the final code.