Updates on Mar 12. 2020.

Some typos fixed

Micro Python core updated to the latest release 1.12

Large amount of changes and additions

Added 'machine.Onewire' module with DS1820 family support

some typos corrected

Added 'machine.PWM' module

Added 'machine.Timer' module

Updated GSM module

Updates and buf fixes in WiFi and mqtt

README.md updated

Some updates in comments, no code changes

Fixed bug in 'os.rename()' function

Updated 'spi' module

Small bug in 'machine_mem.c" fixed