Avoid the use of pointers passing a reference parameter

Change-Id: I8fc4f5ee307bcab6491f3a0e702a5fe546513ee3
Do not return pointers to vector in MediaElement methods

Change-Id: I7b30bb1100207e48e79e0547cb485e3d2e07359d
Avoid string copy in HttpEndPoint

Change-Id: Id7887845a1bd6c60a2ea8ce7a6fa8f6b7c8665ea