Add licence file and headers.

config/caisar-detection-data.conf

config/drivers/marabou.drv

config/drivers/pyrat.drv

config/drivers/saver.drv

lib/nnet/nnet.ml

lib/nnet/nnet.mli

lib/onnx/onnx.ml

lib/onnx/onnx.mli

lib/ovo/ovo.ml

lib/ovo/ovo.mli

licenses/LGPLv2.1

src/autodetect.ml

src/autodetect.mli

src/language.ml

src/language.mli

src/main.ml

src/printers/marabou.ml

src/printers/pyrat.ml

src/prover.ml

src/prover.mli