TriangularFace vertex attributes are now pointers.

While parsing the input file I'll need to create new vertexes with the
"new" operator. As "new" returns a pointer, I won't be able to pass
references to TriangularFace's constructor.

One may say that I could call Vertex's constructor explicitly then pass
the newly created object to the constructor of TriangularFace. That
won't be possible for as the new Vertex goes out of scope its references
will point to invalid memory adresses.
Mesh attributes are now const pointers.

I won't need to access non const methods from TriangularFace.
Parsing routines added to OBJParser.

It can now parse extract meshes from the input file by parsing its
object, vertex and face lines.

Error handling for malformed file will be added in the future.