better place to store temp. generator data

[nesnoj]

The data of agg. genos are currently stored in Network's attribute _dingo_import_data (written by dingo importer, read by geno importer) #21. To avoid spamming our main class, I need a better location here..

EDIT: If we had something like run_edisgo(), the dingo importer could return the data and pass it to the generator importer.

[birgits]

Handling of generators in aggregated areas has changed completely. They are now exported in ding0 the same way as other generators. We can therefore close this issue.