metadata view: introduce a minimal task metadata view

* Bare bones task metadata view.
* Display task metadata, prerequisites and outputs.
* Support for viewing task configuration, broadcasts, etc to follow in
  future PRs.
* Support for markup (e.g. markdown & reStructured text) to arrive in
  future PRs (pending a decision on how to configure the markup
  language).

src/components/cylc/commandMenu/Menu.vue

@@ -222,7 +222,7 @@ export default {
 
   methods: {
     isEditable (mutation, authorised) {
-      return mutation.name !== 'log' && !this.isDisabled(mutation, authorised)
+      return mutation.name !== 'log' && mutation.name !== 'info' && !this.isDisabled(mutation, authorised)
     },
     isDisabled (mutation, authorised) {
       if (!authorised) {
@@ -269,6 +269,23 @@ export default {
             }
           )
         })
+      } else if (mutation.name === 'info') {
+        this.$router.push({
+          name: 'Workspace',
+          params: {
+            workflowName: this.node.tokens.workflow
+          }
+        }).then(() => {
+          eventBus.emit(
+            'add-view',
+            {
+              name: 'Info',
+              initialOptions: {
+                requestedTokens: this.node.tokens || undefined
+              }
+            }
+          )
+        })
       } else {
         mutate(
           mutation,

src/utils/aotf.js

@@ -35,7 +35,7 @@ import {
   mdiDelete,
   mdiEmail,
   mdiFileDocumentOutline,
-  mdiVectorPolylineEdit,
+  mdiInformationOutline,
   mdiMinusCircleOutline,
   mdiPause,
   mdiPauseCircleOutline,
@@ -44,7 +44,8 @@ import {
   mdiPlaylistEdit,
   mdiRefreshCircle,
   mdiReload,
-  mdiStop
+  mdiStop,
+  mdiVectorPolylineEdit,
 } from '@mdi/js'
 
 import { Alert } from '@/model/Alert.model'
@@ -128,6 +129,7 @@ export function getMutationIcon (name) {
     case 'clean': return mdiDelete
     case 'editRuntime': return mdiPlaylistEdit
     case 'hold': return mdiPauseCircleOutline // to distinguish from pause
+    case 'info': return mdiInformationOutline
     case 'kill': return mdiCloseCircle
     case 'log': return mdiFileDocumentOutline
     case 'message': return mdiEmail
@@ -188,6 +190,7 @@ export const primaryMutations = {
     'trigger',
     'kill',
     'log',
+    'info',
     'set'
   ]
 }
@@ -313,6 +316,13 @@ export const dummyMutations = [
     _requiresInfo: false,
     _validStates: WorkflowStateNames,
   },
+  {
+    name: 'info',
+    description: 'View task information.',
+    args: [],
+    _appliesTo: [cylcObjects.Namespace],
+    _requiresInfo: false
+  },
 ]
 
 /**
@@ -322,7 +332,7 @@ export const dummyMutations = [
  */
 const dummyMutationsPermissionsMap = Object.freeze({
   broadcast: Object.freeze(['editRuntime']),
-  read: Object.freeze(['log'])
+  read: Object.freeze(['log', 'info'])
 })
 
 /**