specialize GetMPI_StructAsArray

- specialize GetMPI_StructAsArray for static arrays of math::Vector
extend interface of toString()

- add seperator and enclose symbols to .toString()
output energy field components

output field components of E field and B field
fix copy past bug
change example in comment
Merge pull request #447 from psychocoderHPC/topic-refactorEnergyFields

Energy Fields: Componentwise Energy Calc