Generate time dim if it doesn't exist

[forman]

Expected behavior

Some NC datasets provide time coverage information using attributes time_coverage_start, time_coverage_end but don't define a time dimension and coordinate variable, e.g. Land Cover CCI.

Cate should generate the missing time dimension and coordinate variable if it finds the attributes time_coverage_start, time_coverage_end.

Actual behavior

Some operations raise errors if a dataset is lacking a time coordinate variable.

Merging of many such datasets has been addressed in #575 in order to fix #514 but that is not a general solution as it just adds a time dimension, but not a time coordinate variable.

Specifications

Cate 1.0 - 2.0.dev9

EDIT:

• we must add the time dim when opening datasets from ODP so that timeseries of Land Cover CCI and other ECVs have a time dim

[forman]

Reopen as we always want to add a missing time dim when opening datasets.

[forman]

Prosper said it's closed now.