Replace float/Float with double/Double, add tests get/setValueDouble
Replace getValueFloat with getValueDouble, extend translation range

Internally, use getValueDouble for KNX 2-Byte floats. Also, newer DPTs
of KNX 2-Byte float allow the whole supported value range of that type.
Therefore, use 9.026 (rain amount) for translation, which covers [min
..max] range.
Small documentation update for ctor
Update group addresses of datapoints to match KNX test device, cleanup

Update datapoint addresses, convert local variables to fields. Better
checks for read values.
Allow "break" as substitute for stepcode "0" in strings, with unit test

Support the string literal "break" as human readable substitute for
stepcode 0 on translation from strings. String getters already performed
that substitution.
Don't localize values returned in scientific notation (report and
fix by Snickermicker)

Strings holding bigger floating point values use scientific notation,
which should not get formatted according to the current locale for
consistency.
Add test for non-localized formatted strings of floating point values