add obs_source functions to allow name manipulation and lookup based upon name, and a few other functions related to getting/setting source information

add support for texture_rect texture type in shaders, add new form, clear up a few things in the API

With the permission of my fellow contributors, I'm switching obs-studio back to GPL v2+ to prevent issues between this project and the original OBS project, and for personal reasons to avoid legal ambiguity (not political reasons, I admittedly would prefer GPL v3+)

cleaned up main internal data structure design, changed to reference counting for sources to ensure safe destruction of source objects from all parts of the system, added some service-related stuff for testing

added support for jansson, added new output files, made some adjustments to the API, fixed a UI subclass issue

finish up most of the source audio stuff and rename some variables/structs/enum to be a bit more consistent

fill out the rest of the source video frame functions, added nv12 decompression function, and cleaned up the design of the source video frame stuff

added intial async audio/video code, fixed a few bugs, improved thread safety, and made a few other minor adjustments

change names, fix some bugs, minor GL/D3D fixes, update tests, fix effect files, output a little more debug information