+ added tests and fixed behavior

sqlite does not seem to allow using boolean values in select query

should be tested for all dbms not only cubrid even if the problem may
not exist in all of them it is good to verify that.

http://www.yiiframework.com/forum/index.php/topic/48359-inserting-nulls/page__view__findpost__p__226019

closes #1084

- Better names
- Removed not used MySQLTestCase
- Moved base testcase for DB to db namespace
- Minor style fixes

Appended newlines to every PHP document that did not have a newline as the last character in the file.

Added support for scopes defined in AR classes.

finished AR documentation.