Split EagerCursorTest into unit and functional tests

Functional test for Query preparing an EagerCursor is moved to QueryTest. EagerCursorTest is now all unit tests.
EagerCursor::getSingleResult() should always return first element
EagerCursor::getSingleResult() should return null for no results
Merge pull request #161 from doctrine/1.0.x-eagercursor

Fix EagerCursor::getSingleResult() behavior