examples/radio-observer: Remove duplicate timer initialization
ll: Modify timing parameters to uint32_t
bci: Modify timing parameters to uint32_t
timer: Change timer_start() API from ms to us

In several places we need to have timers with microsecond resolution.
This patch modifies the timer_start() API to accept us, adds helper
macros TIMER_MILLIS() and TIMER_SECONDS(), and updates all examples.
ll: Enforce advertise interval to be multiple of 0.625 ms
ll: Rename pdu_type to type

This patch removes redundant prefix in the advertising type field.
ll: Add scannable advertising

This patch adds support for scannable advertising, sending SCAN_RSP if
SCAN_REQ PDU is received. SCAN_REQ PDUs can be sent by the remote if the
advertiser is sending ADV_IND or ADV_SCAN_IND.
example: Add setting scan response data

This patch changes the ll-broadcaster example to send scannable
advertising PDU, and reply device appearance in the scan response
PDU.
nrf51822/log: Parametrize buffer length
examples: Rename example to radio-passive-observer
build: Add "examples" rule
radio: Remove old radio events documentation
nrf51822/radio: Set inter frame space to 150 us
nrf51822/radio: Add reference for radio mode
nrf51822/radio: Create define to base radio shorts
nrf51822/radio: Remove all not base shorts when stop the radio

This prevents triggering unwanted shorts right after stop the radio.
nrf51822/radio: Fix NULL radio driver bug

The radio should operate normally without a driver.
Update AUTHORS
examples: Sanitize radio examples' timeouts
examples/radio-broadcaster: Reorganize code & comments