If using WIFI_INIT_CONFIG_DEFAULT, error message will point out lack
of WiFi. Otherwise linker errors on WiFi symbols should help give a
clue as to what is broken.
Piggy-backs on changes in !420, ref github #230#237
New makefile component_wrapper.mk allows some variables to be set
before component.mk is evaluated. This properly fixes problems with
sdkconfig being hard to access in all phases of the build.
Including component_common.mk is no longer necessary and will print a
deprecation warning for components which use it.
