Improvements for MC1322/Econotag

Added some new functions for hardware usage on mc1322x. Also enabled 2nd button on platform econotag. I think configure(SENSORS_HW_INIT, 1) in core/lib/sensors.c is for hardware initialisation
while configure(SENSORS_HW_INIT, 0) should disable it. So i changed it. I checked all other
files for compatibility problems, but there is no position, where SENSORS_HW_INIT is used with value:

dev/sht11/sht11-sensor.c
platform/eval-adf7xxxmb4z/button-sensor.c
platform/iris/dev/sensors/battery-sensor.c
platform/z1sp/dev/potentiometer-sensor.c
platform/cooja/dev/pir-sensor.c
platform/cooja/dev/vib-sensor.c
platform/cooja/dev/button-sensor.c
platform/sky/dev/button-sensor.c
platform/sky/dev/temperature-sensor.c
platform/sky/dev/battery-sensor.c
platform/sky/dev/radio-sensor.c
platform/sky/dev/light-sensor.c
platform/seedeye/dev/battery-sensor.c
platform/seedeye/dev/radio-sensor.c
platform/z1/dev/z1-phidgets.c
platform/z1/dev/potentiometer-sensor.c
platform/z1/dev/button-sensor.c
platform/z1/dev/temperature-sensor.c
platform/z1/dev/battery-sensor.c
platform/z1/dev/radio-sensor.c
platform/z1/dev/light-sensor.c
platform/micaz/dev/sensors/battery-sensor.c
platform/avr-raven/button-sensor.c
platform/native/dev/pir-sensor.c
platform/native/dev/vib-sensor.c
platform/native/dev/dummy-sensors.c
platform/avr-atmega128rfa1/button-sensor.c
platform/wismote/dev/battery-sensor.c
platform/wismote/dev/ext-sensor.c
platform/wismote/dev/radio-sensor.c
platform/wismote/dev/light-sensor.c