SDK additions

With some additions to the X-Plane SDK, I think a lot of code could be simplified. Here's what I'd love to have:

1. An API to notify plugins (via callback) of new/existing commands and datarefs would mean I could avoid scanning files in DRT. This is a hack I'd love to get rid of.

   // Called every time a new command is created by a plugin
   typedef void (* XPLMCommandCreation_f)(
       const char *         inCommandName,
       const char *         inCommandDescription,
       XPLMPluginID         inCreatingPlugin,
       void *               inRefcon);
   
   // Register a callback
   XPLMRegisterCommandCreationCallback(
       XPLMCommandCreationCallback_f inCallback,
       void *                inRefcon);
   
   XPLMUnregisterCommandCreationCallback(
       XPLMCommandCreationCallback_f inCallback,
       void *                inRefcon);
   
   
   // Called every time a new dataref is created
   typedef void (* XPLMDataCreationCallback_f)(
       const char *         inDataName,
       const char *         inDataDescription,
       XPLMPluginID         inCreatingPlugin,
       XPLMDataTypeID       inDataType,
       int                  inIsWritable,
       void *               inRefcon);
   
   XPLMRegisterCommandCreationCallback(
       XPLMDataCreationCallback_f inCallback,
       void *                inRefcon);
   
   XPLMUnregisterDataCreationCallback(
       XPLMDataCreationCallback_f inCallback,
       void *                inRefcon);
   

2. Functions to get attributes of commands and datarefs:

   a. Description (as provided in the UI, and DataRefs.txt), etc. The description is often informative for people trying to understand what a dataref found in DRT does. It would also be useful to describe commands to users using this text in the same way that the Settings window does.

   // Get the description of a command/dataref
   int XPLMGetDataRefDescription(XPLMDataRef inDataRef, char *outName, char *outDescription);
   int XPLMGetCommandDescription(XPLMCommand inCommand, char *outName, char *outDescription);
   

   b. Which plugin created a command/dataref. This would simply be informative in DRT, or could be used as a filter in the search window.

   // Which plugin originally created a command/dataref?
   XPLMPluginID XPLMGetDataRefCreator(XPLMDataRef inDataRef);
   XPLMPluginID XPLMGetCommandCreator(XPLMDataRef inDataRef);
   

   c. Check if a dataref is deprecated. The current version of DRT scans DataRefs.txt for the word DEPRECATED for this purpose.

   // Determine if a dataref is deprecated.
   //
   // By the time you have a XPLMDataRef, X-Plane will have already thrown a warning about a
   // deprecated dataref being used. If possible, maybe that warning should be moved to the first
   // time a dataref is read? I suppose this is undesirable for performance reasons.
   //
   // Another way to accomplish this would be to add a new bit in the dataref type flags to indicate
   // if a dataref is deprecated, but that could possibly break existing plugins that can't handle the
   // new bit.
   int XPLMIsDataRefDeprecated(XPLMDataRef inDataRef);
   

   d. Check if a command has been mapped to a keyboard button or joystick. To me this seems like it might be broadly useful. As an example, PlaneCommand needs the user to push a PTT button; if the user hasn't configured it, I could show a helpful dialog explaining the process.

   // Determine if a command is bound to a key or joystick button. This would be useful for plugins
   // that present controls via a command; for example, PlaneCommand needs a PTT button to be bound,
   // and could use this function to determine if we need to present a message guiding the user to
   // bind a key or joystick button to the PTT command.
   int XPLMIsCommandMapped(XPLMCommandRef inCommand);