Finish the rest of the settings dialog code

- Move over the last of the original settings dialog code to QT.  It was
  actually a bit easier to write in the QT version.  wxWidgets was
  definitely not ideal for that because the pages would fully
  create/destroy every time.

- [Win32] Fix os_dlopen so that it only appends .dll if not present

- [MacOS] Fix name dialog text edit widget issue (it would be better if
  we could just use the list widget for editing labels, will have to
  look in to that in the future)

- Tweak the settings UI a bit more and make 30 FPS default

- Add a macro to convert a QString to a UTF-8 const char * string

- Rename build/plugins to build/obs-plugins

- Remove the last of the wxWidgets code