Coding style rules

The following information is intended to improve the quality and readability of the code. Target readers are committers.

Add changes to status.xml

1. Please add all changes to a status.xml (of course there are exceptions like fixing typos etc.)
2. Starting with 2.2 we have separate status files for each block, so if you're changing something in a block, add it to the status.xml of that block and not in the global status.xml.
3. If you're adding something to both, 2.1.x and 2.2, add the change to the status.xml of 2.1 only - all the status files in the 2.2 repository contain only changes from 2.1.x to 2.2.