clean math::vector and DataSpace

- add toString method for math::vector
- rename math::vector.volume method to productOfComponents
- delete all methods in DataSpace which not return a DataDaspace and are defines in math::Vector
use toString to print DataSpace
add changes which were annotated by ax3l
Merge pull request #138 from psychocoderHPC/topic-cleanVector

Refactor Vector/DataSpace implementation