Changes

pysim/log: also accept ANSI strings to specify the log message colors

the PySimLogger class currently only accepts cmd2 color enum values.
This is what we need for pySim-shell.py. However, in case we want to
use the PySimLogger in stand-alone programs that do not use cmd2, this
is a bit bulky. Let's add some flexibility to PySimLogger, so that we
can specify the colors as raw ANSI strings as well.

Change-Id: I93543e19649064043ae8323f82ecd8c423d1d921
Related: SYS#7725