var-dumper component

| Q             | A
| ------------- | ---
| Doc fix?      | no
| New docs?     | yes
| Applies to    | 2.6
| Fixed tickets | none

- [x] general introduction
- [x] cloner doc
- [x] caster doc
- [ ] dumper doc
- [ ] example output
- [ ] enhance the RST (with others, I'm far from a specialist)
I would stop the quick intro after this line and then put the list as normal text. E.g.

````rst
    The VarDumper component provides mechanisms for walking through any arbitrary PHP variable.
    Built on top, it provides a better ``dump()`` function that you can use instead of :phpfunction:`var_dump`.

The advantages of the ``dump()`` function are:

...
````