Updated SimpleTag & DataTag to have only "hasReference" & "removeReference" with "const string &id" parameter.
Fixed TestSimpleTag to use only "const string &id" version of "hasReference" & "removeReference"
Merge pull request #144 from balint42/fix_getter-setter

Final (alpha) fix of getter-setter patterns
Fixed all entity-handling setters to unset field or throw exception if empty entity passed.

The following setters are affected:

EntityWithMetadata::metadata 	(optional => unset field)
DataTag::extents		(optional => unset field)
DataTag::position 		(obligatory => throw runtime error)
Representation::data		(obligatory => throw runtime error)
Section::link			(optional => unset field)

Adressing issue #89
fixed bug in SimpleTagHDF5, implementation of TestRepresentation
Merge pull request #146 from jgrewe/representation

implementation of TestRepresentation and following bugfix in SimpleTag

LGTM
Fixing handling of empty strings by setters.

Adressing issue #89 three principles have been implemented:
-all setters that accept strings now throw a runtime error if the string is empty

The following setters change:

NamedEntity::definition
NamedEntity::name
NamedEntity::type
DataArray::label
DataArray::unit
DataTag::extents
DataTag::positions
RangeDimension::unit (also added "forceUpdatedAt();")
RangeDimension::label (also added "forceUpdatedAt();")
SampledDimension::unit (also added "forceUpdatedAt();")
SampledDimension::label (also added "forceUpdatedAt();")
Property::mapping (also added "forceUpdatedAt();")
Property::unit
Section::mapping (also added "forceUpdatedAt();")
Section::repository (also added "forceUpdatedAt();")
Minor bugfixes to prior commits of this branch.
Added an exception for empty string errors.
Merge pull request #147 from balint42/fix_setters

Fix setters
removed todos and empty lines in Block.hpp
removed todo and minor cleanup in Property.hpp
docstrings for dimension methods
docstrings and reference setters in DataTag

added setter for reference taking the string argument. Interally
methods work with ids not DataArrays.
adding and removing References only with ids. added some documentation

Conflicts:
	include/nix/SimpleTag.hpp
	include/nix/hdf5/SimpleTagHDF5.hpp
addReference externally with id and entity internally string only
rework section interface
createRepresentation interally with id
refactor EntityWithSource
refactor EntityWithMetadata