Add new event to the SDK: wxEVT_CMD_OPEN_PROJ_SETTINGS. this event is sent when a user requests to open the project settings
Fixed: crash when opening the project settings using an accelerator key Alt-F7 or from the main menu bar
Fixed: project settings dialog: don't allow more than one instance opened (the dialog is non modal)
Improved: project settings: instead of writing the project XML directly to file system, write it first to wxStringOutputStream and after that move it to the
  file system. This approach makes the XML writing an instant operation (on huge projects, like LLVM, writing the XML project can take couple of seconds...)