Refactoring some pins definitions.

1. Removing special handling of analog pin as digital.
2. Adding all pins to DigitalPin (in Standard as Tiny, etc).
3. Moving TinyX4 LED pin from D5 to D7. Layout symmetric with TinyX5 and
removes conflict with SPI/MOSI=DO.
Force dependency to count but avoid unnecessary printout.
Fixed documentation.
Improving IOStream, IOBuffer and UART classes.

1. Adding blocking/non-blocking mode. Sleep mode setting on blocking.
2. Mode setting functions; set_blocking/set_non_blocking().
3. New peekchar(c) function to look for a character in buffers.
4. Implementing gets() for UART.
5. Changed flush(); removed mode parameter, use device setting instead.
6. Full example/test suite for IOBuffer (Sandbox/CosaIOBuffer).