* Refactors output format in a way it is (or should at least be) more readable.
(NB.: As source of inspiration, I chose the rustc compiler output.)
* Adds color support to the stream output.
* Also improves multiline source formatting
(i.e. truncating too long lines, like done with single lines already)
* solc: adds flags --color (force terminal colors) and --no-color (disable autodetection)
* solc: adds --new-reporter to give output in *new* formatting (colored or not)
* Changelog adapted accordingly.
