CONTRIB: move halog to admin/

halog is an admin tool, so let's move it to admin/ as well. The makefile
was updated to build from the new directory.
diff --git a/.github/workflows/contrib.yml b/.github/workflows/contrib.yml
index d84c99d..53f6025 100644
--- a/.github/workflows/contrib.yml
+++ b/.github/workflows/contrib.yml
@@ -10,9 +10,9 @@
 
     steps:
     - uses: actions/checkout@v2
-    - name: Compile contrib/halog/halog
+    - name: Compile admin/halog/halog
       run: |
-        make contrib/halog/halog
+        make admin/halog/halog
     - name: Compile dev/flags/flags
       run: |
         make dev/flags/flags