changed handling of reaction pre-exponential units to write converted value to CTML, rather than pass original value with a units string
changed handling of reaction pre-exponential units to write converted value to CTML, rather than pass original value with a units string

Heathckliff/cantera,imitrichev/cantera,Heathckliff/cantera,Heathckliff/cantera,imitrichev/cantera,Heathckliff/cantera,Heathckliff/cantera,imitrichev/cantera,Heathckliff/cantera,imitrichev/cantera,imitrichev/cantera,imitrichev/cantera