Added lua binding for FindAllEntities (#774)

Content/Documentation/ScriptingAPI-Documentation.md

@@ -629,6 +629,7 @@ The scene holds components. Entity handles can be used to retrieve associated co
 - UpdateHierarchy()	-- updates the full scene hierarchy system. Useful if you modified for example a parent transform and children immediately need up to date result in the script
 
 - CreateEntity() : int entity  -- creates an empty entity and returns it
+- FindAllEntities() : table[entities] -- returns a table with all the entities present in the given scene
 - Entity_FindByName(string value, opt Entity ancestor = INVALID_ENTITY) : int entity  -- returns an entity ID if it exists, and INVALID_ENTITY otherwise. You can specify an ancestor entity if you only want to find entities that are descendants of ancestor entity
 - Entity_Remove(Entity entity, bool recursive = true, bool keep_sorted = false)  -- removes an entity and deletes all its components if it exists. If recursive is specified, then all children will be removed as well (enabled by default). If keep_sorted is specified, then component order will be kept (disabled by default, slower)
 - Entity_Duplicate(Entity entity) : int entity  -- duplicates all of an entity's components and creates a new entity with them. Returns the clone entity handle