[cpp] Add -Wall compiler option to root CMakeLists

+ Resolve all warnings

cpp/algorithms/sorting/bubble/lib-bubble.cpp

@@ -15,9 +15,9 @@
 void BubbleSort(std::vector<int> &array)
 {
   // For each value within the set, starting at 0
-  for (int sortedPivot = 0; sortedPivot < array.size(); sortedPivot++) {
+  for (size_t sortedPivot = 0; sortedPivot < array.size(); sortedPivot++) {
     // Check every other remaining value in the set
-    for (int j = array.size() - 1; j > sortedPivot; j--) {
+    for (size_t j = array.size() - 1; j > sortedPivot; j--) {
       // Swap if the value at j is less than the value before it
       if (array[j] < array[j - 1]) {
         std::swap(array[j], array[j - 1]);