Fixed design issues in BPartitionParameterEditor.

* The user of an editor needed knowledge about the editor in order to make
use of it.
* Furthermore, the BPartitionParameterEditor exposed type specific
functionality that it shouldn't know anything about, either.
* We may now define a number of known parameters per editor type; right now
there is only "type" as it's needed by DriveSetup.
* Adapted all disk systems, and DriveSetup to the new API.
* Renamed CreateParamsPanel, and InitializeParamsPanel to *ParametersPanel
in DriveSetup.
* They now share a common base class AbstractParametersPanel.