[TASK] Define abstract methods in upgrade wizards

Adds the commonly used methods checkForUpdate() and
performUpdate() to the abstract definition.

Change-Id: I3584791c9a4a0ab7e79946d604c5d26875299c64
Resolves: #40437
Releases: 6.0
Reviewed-on: http://review.typo3.org/14227
Reviewed-by: Christian Kuhn
Tested-by: Christian Kuhn
Reviewed-by: Oliver Hader
Tested-by: Oliver Hader