Improve null handling
Add test also for other databases
Use char(1) for bit
Fix tests
Exclude test
Merge branch 'master' of github.com:querydsl/querydsl into i921

Conflicts:
	querydsl-sql/src/test/java/com/mysema/query/SelectBase.java
	- imports
Merge pull request #1087 from querydsl/i921

Improve null handling