Merge pull request #333 from phyloref/simplify-specifier

The Specifier component has some complex logic that allows users to modify the properties of a specifier in multiple ways, but this can lead to the specifier being overwritten just be opening it (#263). This PR sets about restructuring this component so that you can no longer modify the specifier just by opening it -- you have to explicitly modify something to trigger a modification action. (This is the minimum we need to close #263).

Now, we can't just remove all of this code, because the way in which Vue Store's data model works, we can't just plug the UI directly into the data object -- we have to call `$store.commit('setSpecifierProps', {specifier, props})` or `$store.commit('replaceTUnitForPhylogenyNode', {...})` to commit the results. So instead we need a model like this:
1. When the component is loaded, we load all of its values into a bunch of local variables, which model fields in the UI (so changing the UI immediately changes these fields). This is handled in the method `loadSpecifier()`.
2. We watch all of these variables; if any of them change, we immediately update the underlying data object with the appropriate variables depending on the specifier type. This is handled in the method `updateSpecifier()`.

Additionally, this PR:
* Removes `Apomorphy` as an option for the specifier dropdown (closes #331).
* Changes the "Expand" button on the specifier to the clearer "Edit" (this still changes to "Collapse" when the editor is expanded).
* Fields that could previously be edited has now been made readonly.
* Renames the "Verbatim specifier" field to the clearer "Specifier label".

Closes #320: we don't include any special support for UUIDs, but we do now note that they can be used. They appear as collection IDs.

src/components/phyloref/PhylorefView.vue

@@ -573,7 +573,7 @@ export default {
     },
     computedPhylorefType() {
       // Return the type of phyloreference based on internal/external specifier structure.
-      return this.$store.getters.getPhylorefType(this.selectedPhyloref);
+      return this.$store.getters.getPhylorefTypeDescription(this.selectedPhyloref);
     },
     phylorefURI() {
       // Get the base URI of this phyloreference.

src/components/phyx/PhyxView.vue

@@ -122,7 +122,7 @@
                   {{ getPhylorefLabel(phyloref) }}
                 </a>
               </td>
-              <td>{{ $store.getters.getPhylorefType(phyloref) }}</td>
+              <td>{{ $store.getters.getPhylorefTypeDescription(phyloref) }}</td>
               <td>{{ (phyloref.internalSpecifiers || []).length }}</td>
               <td>{{ (phyloref.externalSpecifiers || []).length }}</td>
               <td v-for="(phylogeny, phylogenyIndex) of phylogenies">
@@ -498,7 +498,7 @@ export default {
         return [
           this.$store.getters.getPhylorefId(phyloref),
           wrappedPhyloref.label,
-          this.$store.getters.getPhylorefType(phyloref),
+          this.$store.getters.getPhylorefTypeDescription(phyloref),
           // Write out the clade definition.
           phyloref.definition || "",
           // Write out the internal specifier labels