Tests: Add time emulation feature for tests with BEREMIZ_TEST_CYCLES CFLAG.

Adding BEREMIZ_TEST_CYCLES=1000 in a project's CFLAGS will:
- run 1000 cycles with no pause
- emulate time flowing normaly for PLC code
- exit PLC thread

This allows:
- testing standard library blocks that deal with time without having to wait
- unit testing and code coverage with POUs that uses time

#!/usr/bin/env python
# -*- coding: utf-8 -*-

# This file is part of Beremiz
# Copyright (C) 2019: Edouard TISSERANT
#
# See COPYING file for copyrights details.

from __future__ import absolute_import
from svghmi.svghmi import *