Based on extmod/utime_mphal.c, with:
- a globals dict added
- time.localtime wrapper added
- time.time wrapper added
- time.time_ns function added
New configuration options are added for this module:
- MICROPY_PY_UTIME (enabled at basic features level)
- MICROPY_PY_UTIME_GMTIME_LOCALTIME_MKTIME
- MICROPY_PY_UTIME_TIME_TIME_NS
Signed-off-by: Damien George <damien@micropython.org>
