Qt Quick Test: Fix links

To TestCase and SignalSpy. Add link to the QtTest qml module.

Change-Id: Ibbcc90acb2ef81ecaba5d1045b30b373115fb195
Reviewed-by: Topi Reiniö <topi.reinio@digia.com>
Reviewed-by: Martin Smith <martin.smith@digia.com>
Fix some typos in documentation.

Fix some spelling and grammatical errors in comments that show up in Qt documentation. No changes to code.

Change-Id: I2ec9242c0bbb4e66d6c27be6dba8ab0b365bb17f
Reviewed-by: Topi Reiniö <topi.reinio@digia.com>
Reviewed-by: Sze Howe Koh <szehowe.koh@gmail.com>
Merge remote-tracking branch 'origin/stable' into dev

Change-Id: Ie06cc013bf7d6c5a4423ff729599c6fa73d9b416