build: Move Makefile.common to examples directory

This patch moves Makefile.common to examples directory since only the
examples use it.
build: Modify Makefile to allow configure the build

This patch allows the user to configure the build through make command
line. For example:

	$ make CONFIG1=value1 CONFIG2=value2

This defines CONFIG1 and CONFIG2 in all source files with the specified
values.

This is a temporary solution until a better build system is deployed.
nrf51822/log: Add missing newline at ending of file
log: Remove unnecessary do-while loop
log: Add CONFIG_LOG_ENABLE configuration

This patch adds the CONFIG_LOG_ENABLE configuration. Its default value
is active. To deactivate LOG messages, build the library with
CONFIG_LOG_ENABLE=0:

	$ make CONFIG_LOG_ENABLE=0
ll: Remove newline between function call and error check
bci: Remove non-significant advertising data part from in-air packet

Generic Access Profile specification section 11, Core 4.1 page 2023:
"Only the significant part of the Advertising or Scan Response data
needs to be sent over the air."
radio: Posfix radio_handler type with cb
blessed: Rename project from blestack to blessed
blessed: Move public headers to include/blessed
bci: Prefix ENABLE and DISABLE definitions with BCI
nrf51822: Remove hardcoded path to NRF51 SDK

Now, the user needs to provides NRF51_SDK_PATH to the build system. He
can pass it via make command line:

	$ make NRF51_SDK_PATH=/path/to/sdk

Or put it inside Makefile.config (recommended way):

	$ echo "NRF51_SDK_PATH=/path/to/sdk" >> Makefile.config
	$ make

NRF51_SDK_PATH must point to the directory that contains `nrf51822`
path.

Currently, blessed only supports the SDK version 4.4.x.
nrf51822: Allow the user to customize build parameters for his board

Until now, only old versions of PCA10001 evaluation board were
supported. This patch allows the user to reassign some build variables
in order to compile blessed targeting other nRF51822 revisions and
boards models.

This patch wasn't tested with other nRF51822 boards.
ll: Move length-related definitions to ll.h
examples: Use AD structures in examples