Load(): Subsetting along members is not possible.
Currently, Load() has the parameters 'nmember' and 'nmemberobs' which allow to specify a number of members for each experiment and observation, but doesn't allow to pick which members to load, so all must be loaded.
We could code the following behaviour for 'nmember':
- If it receives a single integer N, it replicates it as many times as experiments in 'exp', and will mean that N members will be loaded from each.
- If it receives a vector with different integers, different numbers of members will be loaded from each experiment.
- If it receives a list of vectors, the specified members are loaded.
Same for 'nmemberobs' and 'obs'.