Batch reassignment of sample sets should be based on names, not ids

[percyfal]

Currently batch reassignment of sample sets is based on ids, but for clarity should be based on names. I had a go at this but with the current implementation it is trickier than anticipated. Basically, the individuals_table needs a new column with the current sample set name which is defined in the sample_sets_table. However, the latter is editable and is updated from time to time with new sample sets, which would need propagation to the individuals_table. Currently, the tables are sort of oblivious to each other's existence.

[percyfal]

Draft code (not working correctly though) is available at https://github.com/percyfal/tseda/tree/ssnames

[hannamlmv]

Similar to: hannamlmv#97