Merge branch 'feature/FS1331-real_type' into 'master'

[real_type] use real_type for all norm computations, fix flyspray/FS#1331

I think these are the last places where double has to be replaced. The only remaining places are superlu and umfpack which are not templated and thus are hardcoded to use double.

This patch fixes flyspray/FS#1331

See merge request !2