OifsYearMeanTemporalmap: Monthly instead of Yearly Frames

[valentinaschueller]

--> as with NEMO output, think about a task OifsTimeMeanTemporalmap that has two subtasks OifsYearMeanTemporalmap and OifsMonthMeanTemporalmap. Test how long such a task will take (--> new OpenIFS output format!)

[valentinaschueller]

Also: Deal with coordinate categorization (final time step is in next year already) - it will be difficult to use the same implementation here as with the NEMO tasks

[valentinaschueller]

Also: Deal with coordinate categorization (final time step is in next year already) - it will be difficult to use the same implementation here as with the NEMO tasks

This is actually not the case anymore with the new OpenIFS output.

This task is quite easy to implement now.