Adding a Nucleo thread variant of the blink sketch.
Removing compiler warnings. Removing W5100 interrupt handler.
Improve NTP example sketch; use DNS to get NTP server network address.
First increment of Soft/SPI.
Add support for clock prescale (frequency scaling).
Improving Nucleo/Thread-Semaphore scheduling.

1. Allow signal-resume priority.
2. Introduce Thread::set_idle_mode() for setting of sleep mode.
3. Update CosaNucleoBlink example sketch; use power down sleep mode.
Add capacitor to digram, change RF component, README update
Merge branch 'master' of https://github.com/mikaelpatel/Cosa