harmonize InputOutputPipe

In order to prepare for a configurable channel layout on model/profile
basis first of all things are much easier and more clear to understand
when having all channels using the InputOutputPipe.
It pointed out that Arduino RCLib does define just only a few
InputTypes, but not enough. Moreover the name of some was quite
misleading (FLP, BRK, PIT,...).
therefore we have now dedicated inputs for SW1, SW2, SW3 and POT1.
similar done for outputs:
added AUX1, AUX2, AUX3 and AUX4.
the actual sketch as such has been modified accordingly to use the
proper descriptive names now.
also created an InputOutputPipe for pot1/aux4 (which was not possible
without all those changes)
restructured main loop in order to have clear sections for:
- reading switch status
- reading analog values
- applying DR/EXPO
- refreshing the InputOutputPipes
- prepare channels
- create PPM signal
- run telemetry checks
- check flight timer

next steps will be to prepare some sort of channel alignment
configuration part within the profile like e.g. a string that looks by
default like "AETR1234", but can be changed to e.g. "TEAR4321" or
whatever.
bug fix, code cleanup, new defaults

- preparation for channel order definition on profile-level in config.h
- default expo values in profile 3 changed
- defaults for transmitter voltage warning levels changed, using cell
calculation now
- comments in the main t5x.ino cleaned up to match current
implementation in a better way
- g_PotiA6 renamed to g_Pot1
- moved InputToOutputPipe up to have a more logical order of definitions
- bug: we moved the poti to the inputToOutputPipe, but forgot to assing
input-system to the analog-pin constructor