Clean & remove old code and dependencies

We don't use QtMultimedia and OpenCV_imgproc anymore

Fixes #218
Improve DHT bootsraping reliability

Don't try to spam boostrap nodes, if we've tried enough nodes and none of them worked, chances are our connection is just a little slow, so wait some more before trying even more nodes or we might never see the end of it. May help with #221
Link toxcore and toxav statically

So we don't have to package them separately, since there are no official Tox debian packages on the main archive
Link libsodium

So we don't have to package it separately
Update install target
Add debian packaging metadata
Update Debian Build-Depends