SA should not fail when NPE occurs during connection establishment

SWT may fail when we try to pass `null` value instead of message string.
To prevent this, we must check message from exception for nullness
first.
Refactoring: hide command creation implementation inside OS class
Refactoring: pass whole object into Backend
Refactoring: extract UI options from split Platform interface

Platform interface had three methods that returned constant values in
all implemetnations. So they can be extracted into separate class.
Refactoring: remove coupling between Platform and DefaultConfiguration classes
Microfix: move trailing comment up