TempConv

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   Converts temperatures
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   Form:
   tC = TempConv( from, to ,tI )
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   ------
   Inputs
   ------
   from       (1,1)    Units of tI ('K','R','C','F')
   to         (1,1)    Units of tC ('K','R','C','F')
   tI         (1,:)    Temperature (deg from)

   -------
   Outputs
   -------
   tC         (1,:)    Converted temperature (deg to)

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