FFmpeg Integration - mp4, webm, gif (#624)
    
    * Webm and Gif Export

    

    * added intermediate jpg conversion to save hard drive space

    

    * Started preferences ffmpegPath selection

    

    * grouped ffmpeg files together

    

    * Working with intermediate format

    

    * Fixed running multiple CPU cores for export

    

    * audio works

    

    * all working, need refactoring and error checking

    

    * Changed Qt includes

    

    * revisited Qt includes

    

    * Clean up code, refactor file cleanup, clean up includes

    

    * started gif import

    

    * import working

    

    * Removed import again, fixed export settings being remembered

    

    * import working, bypassed precompute, back to single core export

    

    * clang formatting applied

    

    * added beta warnings in Preferences Popup

    

    * fixed frame flipping and made looping gif default

    

    * added toonzlibs

    

    * added format checks

    

    * added check to help t32bitsrv crash

    

    * sliders for settings are back

    

    * added customizable timeout for ffmpeg

    

    * fixed gif fps and scale for no palette