StyledEdit/DiskUsage/DriveSetup post-hrev46520 fixes

* StyledEdit - make Find/Replace windows non zoomable, select the search
  string view on showing the window for repetitional search;
* Devices - fix plain property list background - to standard one and
  restore read-only state of this pane;
* DriveSetup - remove radio-mode of drive list context popup menu;
* DiskUsage - SetLowColor to parent background to avoid small text
  rendering issue.

Many thanks to Sergei Reznikov for testing and pointing issues out.