Solc command line arguments

Solc now accepts multiple command line arguments.

- Most of the options concern the output of solc.
- Output to both a file and the standard output is possible.
- Unknown arguments are ignored
- Illegal values to arguments produce a legible error explaining to the user what he did wrong.
If the behaviour only depends on the file suffix, I think it would be better to replace `_argName`, `_title` and `_suffix` by a single argument that influences the behaviour and is used to deduce the three strings. From the signature, the three arguments look orthogonal, but they are not.