High level API should support custom endian for each address

[aldas]

See discussion #80

I'd prefer the high-level API for my system, but I need another endian (BIG_ENDIAN_LOW_WORD_FIRST)). Is ist possible to change endian directly for each address. Maybe something like this from your example
->int16(657, 'battery3_voltage_wo','BIG_ENDIAN_LOW_WORD_FIRST')
or is it a must to use the low-level solution for another endian?

[gutschein]

Would be nice, but as the change of the default endian was already very helpfull. It may deserve a line in the help in chapter "Endianness":
"Changing the default endian with adding a line at the beginning: Endian::$defaultEndian = Endian::<needed_endian>;"