Set default locale
Prevents inconsistencies between the application labels/text (no i18n) and ControlsFX labels (i18n)
Default log message pattern must include trailing newline
Needed to separate message from possible error stacktrace
Installation window step (Previous/Cancel|Done) buttons should end in the same state whether action was successful or not
Delay installation start until stage is displayed
So that possibly early dialog windows may correctly be attached to (and displayed right above) the main window
Handle case where installation start failed
'Cancel' button should still allow to cancel action
Added/changed some TODO comments