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/data_structures_and_algorithms/bit-manipulation.py

@@ -0,0 +1,32 @@
+def test(x, i):
+    return x & (1 << i) != 0
+
+
+def set(x, i):
+    return x | (1 << i)
+
+
+def clear(x, i):
+    return x & ~(1 << i)
+
+
+def toggle(x, i):
+    if test(x, i):
+        return clear(x, i)
+    else:
+        return set(x, i)
+
+
+def test_single(x):
+    if x == 0:
+        return False
+    else:
+        return x & (x - 1) == 0
+
+
+print(test(0b1010, 3))
+print('{0:b}'.format(set(0b1010, 1)))
+print('{0:b}'.format(clear(0b1010, 1)))
+print('{0:b}'.format(toggle(0b1010, 2)))
+print(test_single(0b1010))
+print(test_single(0b1000))