adds default shader for GLSL 150

Signed-off-by: tgfrerer <tim@poniesandlight.co.uk>
moving defaultVAO to a more 'default' position

we bind to the default VAO upon start rendering. it is the client's responsibility to restore to the default VAO if she / he wishes to bind their own VAO,
but it is guaranteed that we have the default VAO upon start rendering.

Signed-off-by: tgfrerer <tim@poniesandlight.co.uk>
adds getter methods for vbo index count / vertex count

this is useful if you want to render the vbo but don't have access to it's generator and therefore don't know how many indices / vertices it contains in the GPU

Signed-off-by: tgfrerer <tim@poniesandlight.co.uk>
uses ofVbo.draw() methods to draw ofMesh()

* this mvoes the draw method to the class affected, and reduces code duplication.

Signed-off-by: tgfrerer <tim@poniesandlight.co.uk>
vbo from mesh - mods

* only apply color, normals, texcoords, indices to the vbo if the mesh has them.

* promises for has*() getter functions in ofMesh not to modify the underlying object, so that we can query ofMeshes passed as const ofMesh&, too.

Signed-off-by: tgfrerer <tim@poniesandlight.co.uk>