Adapt to data security regulations

[2maz]

Opens the issue to change impressum to address the now active legal requirements. Might require further additions regarding external hosting, third party services (added also commented template sections). @doudou @planthaber I have disabled google search, as it seems to be out of support anyhow. Likewise feedburner - was that bound to anyone's account?

[planthaber]

Please think of this: https://github.com/rock-core/base-doc/issues/48