Provide input/output descriptions for all operations

All operations are equipped with a short description to explain what they're good for, and how they work in general. More recently, operations can also describe the purpose and expected data format of their input and output slots. (In 6.x-1.0-alpha3, all those pieces of information are displayed in tooltips of the operation blocks.)

Because input/output descriptions haven't been possible from the start, not all of them are filled in yet. So the task at hand is simply to take a look at the operations shipped with Transformations (transformations/operations.*.inc), find inputInfo()/outputInfo() functions that don't handle 'description' as $propertyKey, have a look what the concerned input or output does, and provide a description (similar to the 'label', just with more detail).

This is very easy to code, and can be tackled in bite-size chunks (one input/output at a time, one operation after another) so it's a perfect task to get acquainted with Transformations. Who wants to try a patch? :-]