Implement a symbolic object for the relation "is an element of"

- [ ] naming (e.g. In, MemberOf, Element)
- [x] move this class to the logic module? - no
- [x] latex support and pretty-printing

(on top of the one commit from #7898)
sure

```python
In [1]: i=Symbol('i', integer=True)

In [2]: Contains(i, S.Naturals)
Out[2]: Contains(i, Naturals())

In [3]: ip=Symbol('ip', integer=True, positive=True)

In [4]: Contains(ip, S.Naturals)
Out[4]: True

```