Flint: Improve flint log error

Try to improve the feed back from flint output in order to deal a little more easily with errors occurred in thre flint process.

• Display stdout/stderr from Flint into a logger (disabled by default)
  • When flint is created, it uses subprocess pipes
  • When flint is attached, it uses socket
• Display logs during flint live cycle managed by bliss (enabled by default)
• Plus few things

This new loggers are displayed like other loggers

lslog()

flint                    WARNING
flint.output             WARNING [DISABLED]

Output logger can be enabled like that:

# Enable stderr
import logging; logger = logging.getLogger("flint.output"); logger.disabled = False;
# Enable stderr and stdout
import logging; logger = logging.getLogger("flint.output"); logger.disabled = False; logger.setLevel(logging.DEBUG);

Few proposals:

• It is maybe better to enable flint.output by default, while bliss/flint is not very stable, while it is a dev env, not a production env
• Maybe an helper inside DISPLAY_SCANS could be useful to switch on/off this loggers