logs: implement on the fly parsing of ansi code

grunt and js tools have the habit of using ansi
code a lot, which are ugly inside python log window.
http://en.wikipedia.org/wiki/ANSI_escape_code

This is a simple enough implementation of ansicode parser
which integrates well into buildbot's way of displaying logs

Signed-off-by: Pierre Tardy <pierre.tardy@intel.com>
Merge branch 'ansicodes' of git://github.com/tardyp/buildbot