New cpp folder structure

Signed-off-by: Alexander Borsuk <me@alex.bio>

libs/drape_frontend/animation/interpolation_holder.cpp

@@ -0,0 +1,46 @@
+#include "drape_frontend/animation/base_interpolator.hpp"
+#include "drape_frontend/animation/interpolation_holder.hpp"
+
+#include "base/assert.hpp"
+
+namespace df
+{
+InterpolationHolder & InterpolationHolder::Instance()
+{
+  static InterpolationHolder holder;
+  return holder;
+}
+
+bool InterpolationHolder::IsActive() const
+{
+  return !m_interpolations.empty();
+}
+
+void InterpolationHolder::Advance(double elapsedSeconds)
+{
+  auto iter = m_interpolations.begin();
+  while (iter != m_interpolations.end())
+  {
+    (*iter)->Advance(elapsedSeconds);
+    if ((*iter)->IsFinished())
+      iter = m_interpolations.erase(iter);
+    else
+      ++iter;
+  }
+}
+
+InterpolationHolder::~InterpolationHolder()
+{
+  ASSERT(m_interpolations.empty(), ());
+}
+
+void InterpolationHolder::RegisterInterpolator(BaseInterpolator * interpolator)
+{
+  VERIFY(m_interpolations.insert(interpolator).second, ());
+}
+
+void InterpolationHolder::DeregisterInterpolator(BaseInterpolator * interpolator)
+{
+  m_interpolations.erase(interpolator);
+}
+}  // namespace df