Check --notify-work values are URLs on start

Currently, the below command works without any error or warning.
```sh
./codechain --notify-work 127.0.0.1:3333 ...
```

But actually, it should be like:
```sh
./codechain --notify-work http://127.0.0.1:3333 ...
```

Start at the command-line handling for --notify-work in the ./codechain entry point and inspect how its value is parsed. Check the behavior for 127.0.0.1:3333 and http://127.0.0.1:3333; done means malformed non-URL values produce an error or warning while valid URLs continue to work.

Written by the indexing model from the issue text.