Add andThen on all optics

[julien-truffaut]

Optics and functions compose in the same way

def compose[A, B, C](f: B => C, g: A => B): A => C
def compose[A, B, C](f: Optic[A, B], g: Optic[B, C]): Optic[A, C]

You may have noticed that the parameters of optics composition are the inverse of function composition. Optics composition looks more like andThen than compose.

def andThen[A, B, C](f: A => B, g: B => C): A => C

Therefore, I propose to create a new overloaded method andThen and deprecate all thecomposeX methods later.

For example for lenses will have something like:

trait PLens[S, T, A, B] {
  def andThen[C, D](other: PLens[A, B, C, D]): PLens[S, T, C, D] = ???
  def andThen[C, D](other: PPrism[A, B, C, D]): POptional[S, T, C, D] = ???
  def andThen[C, D](other: PIso[A, B, C, D]): PLens[S, T, C, D] = ???
  // and so on
}

I propose to overload andThen instead of using andThenLens, andThenPrism for a few reasons:

1. it is more concise
2. users don't need to think about what type of optics they are composing
3. the main reason to have non-overloaded compose methods is to help type inference for optics like at, index, each which I think we can get away by adding shortcuts on each optic Add shortcut for at #956

If this works well, we can deprecate all composeLens, composePrism, ... methods.

[julien-truffaut]

I have started to work on this