The so-called @-syntax inspired by http://jcommander.org/#Syntax

### At-syntax for fetching option values from files

This pull request brings the At-syntax from JCommander to args4j. The syntax is depicted here:

```
java Cmd @/tmp/opts
```

@/tmp/opts is a text file with the options separated by line breaks:

```
-key
value
-variable
value
```

The JCommander version can be viewed here:

http://jcommander.org/#Syntax