Support per-stream resolution settings.

The code now automatically resizes as required.

This change also disconnects camera resolution settings from MJPEG
stream connections; setting the camera resolution can now only be done
via code.

src/default_init_allocator.h

@@ -0,0 +1,38 @@
+// From: http://stackoverflow.com/questions/21028299/is-this-behavior-of-vectorresizesize-type-n-under-c11-and-boost-container
+// Credits: Casey and Howard Hinnant
+#ifndef DEFAULT_INIT_ALLOCATOR_H_
+#define DEFAULT_INIT_ALLOCATOR_H_
+
+#include <memory>
+
+namespace cs {
+
+// Allocator adaptor that interposes construct() calls to
+// convert value initialization into default initialization.
+template <typename T, typename A = std::allocator<T>>
+class default_init_allocator : public A {
+  typedef std::allocator_traits<A> a_t;
+
+ public:
+  template <typename U>
+  struct rebind {
+    using other =
+        default_init_allocator<U, typename a_t::template rebind_alloc<U>>;
+  };
+
+  using A::A;
+
+  template <typename U>
+  void construct(U* ptr) noexcept(
+      std::is_nothrow_default_constructible<U>::value) {
+    ::new (static_cast<void*>(ptr)) U;
+  }
+  template <typename U, typename... Args>
+  void construct(U* ptr, Args&&... args) {
+    a_t::construct(static_cast<A&>(*this), ptr, std::forward<Args>(args)...);
+  }
+};
+
+}  // namespace cs
+
+#endif  // DEFAULT_INIT_ALLOCATOR_H_