Contain direction in `core` package is wrong for formal logic and math

Now we have `Contain` link, that is going from `container` to `conteined`.

That means that for example if container is set A, we have:
```
{
A ↦ 1,
A ↦ 2,
A ↦ 3,
A ↦ 4,
}
```
That leads to a contradiction, that ` A ↦ 1` and `A ↦ 2` cannot exist at the same time, thus it is not possible to combine them into a single function.

On the other hand, if we change the direction:
```
{
1 ↦ A,
2 ↦ A,
3 ↦ A,
4 ↦ A,
}
```

We can correctly define a set using links, and we have function `f(element) = A` for `element = 1, or 2, or 3, or 4`.

The name `Contain` also implies that it goes from `container` to `conteined`, that means we need not only another direction, but also need different name for new link type for example `IsContainedBy`.

`IsContainedBy` will go from `conteined` to `container` and it will be aligned with current math traditions.