Add custom groups to local labels

[StephenChan]

Essentially, allow a source to define its own functional groups. Instead of having a database object per custom group, we'd keep it simple by representing custom-group names as strings. Each LocalLabel would have a 'custom group' string field, and if two labels have the same custom-group string, then they're in the same group.

Or, staying with our original idea for this feature, we could have 3 custom group fields, corresponding to 3 different custom group schemes that each source can define.

The extra string field(s) should be accounted for in the following pages:

• Labelset import
• Labelset export
• Edit labelset entries
• Labelset view (list of labels)

And to actually be useful, custom groups should be usable for any of the same things that functional groups are:

• Showing machine classifier performance by group (e.g. in a confusion matrix)
• Exporting image covers by group (see #40 )
• Statistics (when that's fixed; see #85 )
• (Maybe) Grouping label buttons in the annotation tool

In these cases there would need to be an option to use either functional groups, custom group set 1, custom group set 2, or custom group set 3.

One interesting application is being a substitute for a label hierarchy (#165 ). For example, have labels for coral species, custom group set 1 specifying coral genera, and custom group set 2 specifying coral families.

[StephenChan]

+1 for this based on a recent question via email.

One example motivation: by my understanding, Millepora and Heliopora can be considered part of coral reefs' structure, but in terms of biological taxonomy they are not Scleractinian "hard corals". Depending on what exactly one is interested in counting, one could argue for grouping these with hard coral or with other invertebrates (we currently go with the latter).

[StephenChan]

Another +1, mainly for grouping label buttons in the annotation tool.

We use CoralNet as a monitoring tool, and not on a stony coral reef area.

We have soft corals, and other members of the Cnidaria philum. We have alot of algea, but we also have Bryozoa and invertabrates

Do we have a option to add functional group, or to edit their colors and order on the label list?

Right now, the Dendronephtya (soft coral) and the sponges (Porifera), ascidians and bryozoa are all in the same label-color, and the soft coral is far from the hard coral in its location