Python v3, support new LTV-Website, multi-thread

New version requires Python v3.
Now supports the new LTV-website, which does not, yet, require login. I'll try to implement the login before they start requiring again.
It now uses 1 thread to search for videos and 5 worker threads to search and download subtitle, making it blazingly faster than previous version. The number of threads can be increased, but I left it at 5 for respect for LTV servers.
Slightly improved printed output.