KNX binding should use different mapping of PercentType

KNXCoreTypeMapper maps Openhab's PercentType to KNX's DPT_PERCENT_U8 and vice versa. PercentType holds values from 0% to 100%, but DPT_PERCENT_U8 can hold values from 0% to 255%, where byte 0xff is 255%. 
A better match is DPT_SCALING (5.001) which translates byte 0xff to 100%.
DPT_PERCENT_U8 should be mapped to DecimalType to allow values larger then 100%.
So, 5.001 and 5.004 should now behave as spec'd in KNX Spec.