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

data_structures_and_algorithms/knapsack-0-1.py

@@ -1,38 +0,0 @@
-import unittest
-from math import floor
-
-
-def knapify(xs, capacity=None):
-    assert capacity is not None
-    n = len(xs)
-    # For 0/1 Knapsack, we must use a table, since this will encode which values
-    # work for which items. This is cleaner than including a separate data
-    # structure to capture it.
-    maxes = [[0 for x in range(capacity + 1)] for x in range(n + 1)]
-
-    # Build table maxes[][] in bottom up manner
-    for row in range(n + 1):
-        for col in range(capacity + 1):
-            if row == 0 or col == 0:
-                maxes[row][col] = 0
-            elif xs[row - 1][0] <= col:
-                maxes[row][col] = max(
-                    xs[row - 1][1] + maxes[row - 1][col - xs[row - 1][0]],
-                    maxes[row - 1][col])
-            else:
-                maxes[row][col] = maxes[row - 1][col]
-
-    return maxes[-1][capacity]
-
-
-################################################################################
-# Tests
-################################################################################
-class Test(unittest.TestCase):
-    def test_one_cake(self):
-        actual = knapify([(3, 10), (2, 15), (7, 2), (12, 20)], capacity=12)
-        expected = None
-        self.assertEqual(actual, expected)
-
-
-unittest.main(verbosity=2)