`Json::Reader` has been deprecated for some time, so we replace it with
`Json::CharReader` generated by a `Json::CharReaderBuilder`, or (in the
one instance where we have a stream as input) `Json::parseFromStream();`
- each class is now responsible to free whatever it allocates
- all tests passed on my machine with ffmpeg 3.2
- Clip is now more careful about freeing a reader if it allocated it as well
* Limit max size of preview to the timeline size (this renders very small profiles correctly)
* Fixing CRF quality setting to allow "low" quality without breaking
* Integration of libresvg SVG library (optional during build)
* Major refactor of max_width and max_height for preview optimization
* Fixed many bugs related to preview resizing, with regards to cached frames
* Updating gitlab CI to find RESVGDIR correctly for windows, and adding svgz support
* Updating cmake findresvg module to search for windows locations first, to prevent an issue on our windows builders and updating some CMake output.
* Removing folder path from resvg header, since it could be installed in different named folders. This is an attempt to fix Windows include issues.
* Making call to AV_FREE_FRAME conditional for non windows systems (because it crashes on Windows for seemingly no reason). Needs more investigation.
