Optimize CaloFutureRawToDigits

• amalgamate header into source file
• move verbose printout out of loop
• decode pairs of ADCs per loop iteration, with a separate check whether an odd number of ADC is required,
• use enum instead of string as property
• prefer boost::containers::small_vector over std::vector
• reduce size of flags enum, and make it strongly typed
• remove unused property
• remove unused includes

Ref updates are in Brunel!1012 (merged)