ARM: software serial port integration (Tx only)

- be careful charging functionality not tested
- work corectly with baud rate 19200 and lover
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- TMR2 is used for Tx timing
- ADC for temp is disabled when Tx soft serial is active (maybe timing problem for other functionality)
- some logic are added for enable/disable some funcionality when eternal temp or Tx serial is active (probably not enough)
I'm not sure but maybe most of thous variables/functions  shouldn't be "visible" outside of  TxSoftSerial.cpp?