Authentication documentation needs update

Need detailed description on how to obtain token "by external program". There is no single example how to implement this.

I tried to pass token refresh script as an argument like: restler test --no_ssl --grammar_file Compile/grammar.py --dictionary_file Compile/dict.json --token_refresh_interval 7200 --token_refresh_command "sh token.sh" but it always fails, in logs: "Exception refreshing token with cmd sh token.sh. Error: invalid syntax (, line 1)"