- Implemented document creation with a predefined key.
- Extended DocumentBasicTest.php with a test for this

Signed-off-by: Frank Mayer <frank@frankmayer.net>
Bumped PHP Client API Version to 1.2.0

Signed-off-by: Frank Mayer <frank@frankmayer.net>
Updated CHANGELOG

Signed-off-by: Frank Mayer <frank@frankmayer.net>