Merge branch '2261_multiedit'

Merge branch '2261_multiedit'

* 2261_multiedit: (29 commits)
  Set fullscreen layout as previous editor look'n'feel.
  Updated documentation.
  Open several files in mc editor from command line.
  Show top opened file in screen list.
  Add icons to close window and toggle window state using mouse.
  Skin support for window frames.
  Add toggle fullscreen mode of editor windows.
  Handle CK_ShowNumbers action in dialog level instead of widget one.
  Handle CK_ShowTabTws and CK_ShowMargin actions in dialog level instead of widget one.
  Handle CK_SyntaxOnOff action in dialog level instead of widget one.
  Modify CK_Refresh command handling.
  Handle CK_Option action in dialog level instead of widget one.
  Assign button bar to the current editor.
  Switch windows using keyboard.
  Open each file in its own window.
  Add edit_add_window() function.
  Add CK_Close action to close current open file.
  Handle CK_Shell, CK_LearnKeys, CK_OptionsSaveMode and CK_SaveSetup actions in dialog level instead of widget one.
  Handle CK_Help, CK_Quit and CK_About actions in dialog level instead of widget one.
  Allow move and resize edit window using keyboard.
  ...