Revisit validation

EditorService
- Tests added (verifying validation of graph)
- Moved some messages to constants
- Altered validation to make full use of promises (rather than promises
  to a certain depth then async)
- More validation rules related to fan-in/out scenarios

graph-to-text
- Adjustments to cope better with 'bad input' and try to create some
  kind of graph (tests added for this case)

RenderService
- Prevents creation of tap links from destinations (channels/taps)
- Prevents link switching working for links from destinations

text-to-graph
- Fixed handling of map (use setter)

markup
- no bullet lists on error tooltips if only one entry
- tooltips working for destinations

Fixes #395

Author: aclement

ui/src/app/streams/flo/decoration/decoration.component.html

@@ -6,7 +6,7 @@
 </svg:g>
 
 <template #markerTooltip>
-  <div>
+  <ul class="marker-tooltip">
     <li *ngFor="let msg of getMessages()">{{msg}}</li>
-  </div>
-</template>
+  </ul>
+</template>

ui/src/app/streams/flo/decoration/decoration.component.scss

@@ -1,7 +1,26 @@
 .error-marker-tooltip .tooltip-inner {
   background-color: red;
   max-width: 400px;
+  padding: 2px;
 }
+
 .tooltip.error-marker-tooltip .tooltip-arrow {
   border-right-color: red;
 }
+
+.marker-tooltip {
+
+  list-style-type: none;
+  margin: 0;
+  padding: 0;
+
+  li {
+    border-bottom: 1px solid white;
+    text-align: left;
+  }
+
+  li:last-child {
+    border: none;
+  }
+
+}