Name is set for all scalars, even if not used

[jnnr]

Since #281, the name is automatically set when building the datapackage. The name is necessary because each oemof.tabular component has to have a name. Some entries in additional_scalars get a name, too, even if the name is not used for anything.

There are several options to handle this:

• Exclude some data when the name is set in build_datapackage, e.g. those data whose "region" is "TOTAL".
• Handle the constraints as facade classes with names, too. This can happen as soon as oemof.tabular allows to save constraints as part of the datapackage (Not possible to save constraints as part of the datapackage oemof/oemof-tabular#40)