Topic adiostotxt

According to Issue [#299](https://github.com/ComputationalRadiationPhysics/picongpu/issues/299) I added the possibility to use splash2txt to print out the content of your adios files to txt files. (thanks to f-schmitt for your help :smile: )
Please make all preprocessor commands (`#if/#endif`) start at column 0 (very left).
This is common practise and makes it much easier to read.