Check if saio should replace ego.io

[khelfen]

As discussed we should check if we can replace ego.io with saio. At the moment ego.io is used as database connection with the OEP.

[birgits]

The new data imports are done with saio. As soon as the eGon data is uploaded to the OEP we can remove the old functions and get rid of ego.io. I added it to the list in #358 and therefore will close this issue.