Tidy up structure of briefcase

I had a spare fifteen minutes and decided that I should tidy up my
monorepo. The work of tidying up is not finished; this is a small step in the
right direction.

TL;DR
- Created a tools directory
- Created a scratch directory (see README.md for more information)
- Added README.md to third_party
- Renamed delete_dotfile_symlinks -> symlinkManager
- Packaged symlinkManager as an executable symlink-mgr using buildGo

scratch/deepmind/part_two/package.json

@@ -0,0 +1,15 @@
+{
+  "name": "deepmind-part-two",
+  "version": "1.0.0",
+  "description": "Practicing coding interview questions",
+  "main": "index.js",
+  "scripts": {
+    "test": "echo \"Error: no test specified\" && exit 1"
+  },
+  "author": "William Carroll",
+  "license": "MIT",
+  "devDependencies": {
+    "ts-node": "^8.6.2",
+    "typescript": "^3.7.5"
+  }
+}