**Use case**

Viewing binary data such as bitmasks, hashes, internal representation of IEEE-754 numbers, etc.
Mostly for debugging.

**Describe the solution you'd like**

Similar to `hex`/`unhex`.

`bin` - returns a string with `0` and `1`. Bits are in "human" order, most significant first. Most significant zero bits are not printed (except the case with single zero).

**Describe alternatives you've considered**

Now I have to run interactive `python` from command line, but I will be more happy using ClickHouse.

**Caveats**

The name `bin` may suggest that the function will "split data into bins" but it is completely unrelated.
auto col_res = ColumnString::create();
            ColumnString::Chars & out_vec = col_res->getChars();
            ColumnString::Offsets & out_offsets = col_res->getOffsets();
            const ColumnString::Chars & in_vec = col->getChars();
            const ColumnString::Offsets & in_offsets = col->getOffsets();
            size_t size = in_offsets.size();
            out_offsets.resize(size);
            out_vec.resize(in_vec.size() / 2 + size);
            char * begin = reinterpret_cast<char *>(out_vec.data());
            char * pos = begin;
            size_t prev_offset = 0;
            for (size_t i = 0; i < size; ++i)
            {
                size_t new_offset = in_offsets[i];
                unhexOne(reinterpret_cast<const char *>(&in_vec[prev_offset]), reinterpret_cast<const char *>(&in_vec[new_offset - 1]), pos);
                out_offsets[i] = pos - begin;
                prev_offset = new_offset;
            }
            out_vec.resize(pos - begin);
            return col_res;
        }
        else
        {
            throw Exception("Illegal column " + arguments[0].column->getName()
                            + " of argument of function " + getName(),
                            ErrorCodes::ILLEGAL_COLUMN);
        }
    }
};
class FunctionChar : public IFunction