diversity related processes only run for one channel element

[d4straub]

Diversity related processes produce results only for the first of several files in the input channel "qiime_diversity_core_for_*", because there is only one element in the second input channel "ch_metadata_for_*".
This is true for the following processes:
alpha_diversity
beta_diversity
beta_diversity_ordination

[d4straub]

process beta_diversity still only processes one input file. Possibly because of an additional input value, a simple ".combine" to the input channel doesnt appear to work here.

[d4straub]

Now all diversity related processes use all elements of the input channels correctly.