Fgh002.1: Workflow to test Docker Hub Login in this repo (#675)

* Complete revamp of the buildRelease and buildDocker workflows for Medley.  Also adding the buildReleaseInclDocker composite workflow.

* Add testLogin workflow to test Docker Hub login.

.github/workflows/testLogin.yml

@@ -0,0 +1,23 @@
+name: 'Test Docker Login'
+
+# Run this workflow on ...
+on:
+  workflow_dispatch:
+
+defaults:
+  run:
+    shell: bash
+    
+
+jobs:
+
+  login_test:
+    runs-on: ubuntu-latest
+    steps:
+      - id: only_step
+        uses: docker/login-action@v1
+        with:
+          username: ${{ secrets.DOCKER_USERNAME }}
+          password: ${{ secrets.DOCKER_PASSWORD }}
+
+