Files that do not require compilation and/or 
complex processing before being populated into the root FS.

The features-common.txt contains a common set of features applicable to all
the platforms. During the build it is extended with the platform specific
features.txt from the platform subfolder (if it exists). For lede_generic
the platform specific features might depend on the hardware kind and
the feature set is further extended by adding (if it exists) the
features-<HW_kind>.txt from the lede_generic platform subfolder.

The features are exposed to the unum code during the compilation through
defines in the format:
FEATURE_<upcase_feature_name_w_dashes_turned_to_underscores>
example:
my-feature => FEATURE_MY_FEATURE
See .../src/unum/Makefile for the list of features that affect the agent build.

The release_properties.json is the JSON template for reporting the features
to the server side when publishing the firmware.

As of now features-router.txt does n't have any references, but it is needed
for the external builds to refer to a typical router feature set