Add endpoints for extracting the data needed by CSV_EXPORT.

[TerryHannant]

Initial rough implement

fixes #168

[ertomatic]

Can one of the admins verify this patch?

[berland]

You may want have a peek at https://github.com/equinor/ecl2df/blob/master/ecl2df/summary.py#L299 as well, this is a summary-to-CSV python API I wrote and maintained up until now. If not for staring at the engineer-code, at least for getting an idea of potential traps. At least there is an already set of "frequency"-strings supported in there.

[TerryHannant]

You may want have a peek at https://github.com/equinor/ecl2df/blob/master/ecl2df/summary.py#L299 as well, this is a summary-to-CSV python API I wrote and maintained up until now. If not for staring at the engineer-code, at least for getting an idea of potential traps. At least there is an already set of "frequency"-strings supported in there.

That looks very useful for the frequency handling logic