New option: mute-some-output

The fact Soot prints alotsa things to stdout by default is painful for elegant logging. I added some crude switch for muting some of the outputs (with printable usage and all). The switch could then be later become more powerful: the `G.out` `PrintStream` to which soot prints could have some logic filtering outputs depending on the muting. And you know what would be really awesome? using `slf4j` logging interface ;]