Re: New lisp library -- cell.el

[Zhu Zihao <all_but_last@163.com>]

I push some commits to take the refactor. Check newest at
https://github.com/cireu/emacs-cell/blob/master/cell.el

Changelog:

1. Remove cell-option. Add cell-some, which can be united with nil to present a
nullable value.

2. Unify the name of constructor of cells

- cell-some(new)
- cell-box-make -> cell-box,
- cell-weak-make -> cell-weak

Internal constructors names:

- cell-some--make(new)
- cell-box--make(unchanged)
- cell-weak--internal-make -> cell-weak--make

3. Remove destructuring macro cell-option-if-let and cell-option-when-let, add
pcase pattern cell-some. It's better to extend pcase than a new macro.

4. Remove cell-option related utils.