use optional for getters of definition and name
Sampled dimension returns optional<double> for the offset.
documentation of the Dimensions.
Merge branch 'master' of https://github.com/G-Node/pandora

Conflicts:
	include/nix/base/INamedEntity.hpp
	include/nix/base/NamedEntity.hpp
	include/nix/hdf5/NamedEntityHDF5.hpp
fix
Merge pull request #103 from jgrewe/master

Again, the getter for optional fields plus documentation work on Dimensions
Implemented "method(const none_t t)" pattern for all instances in "DataArray"
Implemented "method(const none_t t)" pattern for all instances in "DataTag", removed "remove*" methods
Corrected use of "method(const none_t t)" in "DataArray" to only exist for really optional types
Implemented "method(const none_t t)" pattern for all instances in "Dimensions"
Corrected errors in 'Dimensions' and 'DataTag'
Implemented "method(const none_t t)" pattern for all instances in "Properties"
Implemented "method(const none_t t)" pattern for all instances in "Sections"
Implemented "method(const none_t t)" pattern for all instances in "SimpleTag"