Add name-to-index function to CanteraObjects for species identification

Implement the capability to obtain the index of a species given that species' name.

The most straightforward solution is to include <boost/algorithm/string/predicate.hpp> for a case-insensitive string comparison (important because some mechanisms use lower-case and others upper-case) and simply loop through all species in CanteraObjects until the specified one is found:

int species_name_to_idx( const std::string speciesName )
{
  bool foundIt = false;
  int idx = 0;
  while( !foundIt ){
    if( boost::iequals( CanteraObjects::species_name( idx ), speciesName ) ) foundIt = true;
    else{
      foundIt = false;
      ++idx;
    }
    if( idx == CanteraObjects::number_species() ){
      throw std::runtime_error( "could not find species with name " + speciesName );
    }
  }
  return idx;
}

This would enable the following code to initialize mole fractions for any mechanism input.

const int fuelIdx = species_name_to_idx( fuelName );
const int oxyIdx  = species_name_to_idx( "o2" );
const int n2Idx   = species_name_to_idx( "n2" );

*XPtr[oxyIdx]  <<= 1.0;
*XPtr[fuelIdx] <<= fToORatio;
if( !oxygenBool ) *XPtr[n2Idx] <<= 3.73;
else *XPtr[n2Idx] <<= 0.0;

fracSum <<= *XPtr[fuelIdx] + *XPtr[oxyIdx] + *XPtr[n2Idx];