Add support for multiple input files

[hopugop]

When copying over the original file, it would be good to be able to pass several mkv files to the script (full paths or *.mkv, etc), and it would iterate over each of them performing the work.

[ghost]

just leaving this here (it loops 4 times and convert+remove all dts streams to ac3):
for ((n=0;n<5;n++)); do find . -type f -iname '*.mkv' -exec mkvdts2ac3.sh -w . -n {} \;; done