Collections updates

Replace "collection" with "collections" in various file names since
we typically use the plural form in conversation and documentation.

Add set() and removeAt() methods needed for collection interfaces. Also
add the KeyedIterable and KeyedIterator interfaces.

Add __construct() methods for collections

hphp/runtime/base/array/array_iterator.cpp

@@ -19,7 +19,7 @@
 #include <runtime/base/array/hphp_array.h>
 #include <runtime/base/complex_types.h>
 #include <runtime/base/object_data.h>
-#include <runtime/ext/ext_collection.h>
+#include <runtime/ext/ext_collections.h>
 
 namespace HPHP {
 ///////////////////////////////////////////////////////////////////////////////
@@ -76,24 +76,6 @@ void ArrayIter::reset() {
   decRefObj(obj);
 }
 
-void ArrayIter::begin(CVarRef map, CStrRef context) {
-  try {
-    new (this) ArrayIter(map.begin(context));
-  } catch (...) {
-    m_data = nullptr;
-    throw;
-  }
-}
-
-void ArrayIter::begin(CArrRef map, CStrRef context) {
-  try {
-    new (this) ArrayIter(map.get());
-  } catch (...) {
-    m_data = nullptr;
-    throw;
-  }
-}
-
 template <bool incRef>
 void ArrayIter::objInit(ObjectData *obj) {
   assert(obj);