Added example + updated existing examples

[StasFainer]

1. Added example "Vanishing point".
2. Changed existing example "Rochester cloak".
3. Changed text and added "description" field to existing examples - "Rochester cloak" and "Aplanatic points".

[StasFainer]

While creating the two simulations with the pencil, I thought that a nice tool would be something similar to the "Beam" tool, but instead of parallel rays to have point sources along the line.
This will make the "Vanishing point" and pencil examples more interactive for the user.

Also, in such tool, an option of having the point sources equidistant along a circle could be interesting too, for example to see how such circle transforms under different optical systems, such as an ideal lens, etc.

[ricktu288]

While creating the two simulations with the pencil, I thought that a nice tool would be something similar to the "Beam" tool, but instead of parallel rays to have point sources along the line. This will make the "Vanishing point" and pencil examples more interactive for the user.

Also, in such tool, an option of having the point sources equidistant along a circle could be interesting too, for example to see how such circle transforms under different optical systems, such as an ideal lens, etc.

#56