Reworked label callbacks

* they are now built at the same time as we build the other event data, so we don't have to jump through another set of if-then hoops
* they are stored as an array, so that they fire in the order intended
Allow late initialization of midi devices, misc debug cleanup

* midi devices can now be initialized via "new" or later via "SetMidiInDevice"
* this opens us up for having a midi device selection menu
* removed stray debugging message from last change
* added ability to send event debug info to any listening windows debugger
* reworked tooltip event debugging
Changing public global variables

* removed underscore prefix to signify that these are ok to interact with outside the library