When adding new links to vidl, it will now put them in a queue (file)
from which it then begins downloading links one after the other. Only
one downloading instance of vidl will ever be running, but you can still
add more links by invoking it again while it is.
Added one new command line option `-c` to quickly empty the queue and
start over.
Fixes#8.
Marty Oehme
3e00e84319
