Changes file for 1.2.2

- Qt 5.1 help documents included.
- Incorrect overwriting of the environment setting value on every
  build/run removed. (QTVSADDINBUG-159)
- Links in Qt help not working, fixed. (QTVSADDINBUG-160)

Change-Id: Ia86b2dec7467277f409820ad0744195856379075
Reviewed-by: Ismo Haataja <ismo.haataja@digia.com>