Unix binary gets tab completion and builtin upip, and more.

py core:
- allow to compile without needing git to extract version
- conform to CPython's way of printing nan/inf with padding
- wrap qstr defs in quotes to protect from C preprocessor
- add stack check to mp_iternext to catch nested iterators
- implement implicit cast to obj for viper load/store index/value
- implement native multiply operation in viper emitter
- expose KeyboardInterrupt in builtins module
- fallback to stack alloca for Python-stack if heap alloc fails
- support unicode (utf-8 encoded) identifiers in Python source
- implement second arg for math.log (optional value for base)
- support mpz bignums in divmod builtin

extmod:
- add ubinascii.unhexlify
- swap address and descriptor args in uctypes constructor

lib:
- fix some issues with dates prior to 1 Mar 2000
- implemente delete key in readline

tools:
- pyboard.py: allow pyboard constructor to take a baudrate parameter
- pyboard.py: change logic for when raw ">" prompt is parsed
- add codestats.sh to compute code statistics such as size, speed

unix port:
- add option to use uPy readline and enable by default (adds tab completion)
- include upip as frozen module within standard uPy executable; standard
  way to use is: micropython -m upip install <module>
- allow to cat a script into stdin from the command line
- make micropython -m <module> work for frozen modules

windows port:
- implement mp_hal_xxx functions and enable uPy readline

stmhal port:
- raise error if disk is full when writing a file
- implement sys.stdin.buffer, sys.stdout.buffer for raw byte mode
- remove all PYBVxx defines and use general config vars instead
- add support for UART5 if MCU has it
- fix slow SPI DMA transfers by removing wfi from DMA wait loop
- break immediately from USB CDC busy wait loop if IRQs disabled
- make I2C transfers use DMA when possible (when IRQs are enabled)

cc3200 port:
- add os.rename()
- add Timer module
- add uhashlib with SHA1 and SHA256
- add ubinascii module
- implement full set of wake-on-WLAN features
- remove NIC abstraction layer
- improve WDT
- make peripheral API more similar to stmhal's
- improve reliability of ftp and telnet servers
- add antenna selection feature to WLAN
- add sendbreak method to UART

esp8266 port:
- add uos module
- allow to set CPU frequency to 160MHz using pyb.freq
- add pyb.ADC class
- to esp module add: mac, phy_mode, sleep_type, deepsleep, flash_id
- update SDK to version 1.1.0 (MIT licensed)
- fix lost chars when transfering large amounts of data over UART
- add skeleton "network" module with bare WLAN() constructor
- add WLAN.connect/disconnect functions
- change esp_scan to keep the current WiFi operating mode

docs:
- document esp module
- allow to generate separate docs for each port (using ..only directive)
- add initial docs for the WiPy