[WIP] input: move border styles from .input__box to .input (closes #548)

Closes https://github.com/bem/bem-components/issues/548
You could compare it here (<a href="http://bem.persidskiy.me/pr-547/desktop.tests/input/simple/simple.html" target="_blank">before</a> / <a href="http://bem.persidskiy.me/pr-549/desktop.tests/input/simple/simple.html" target="_blank">after</a>)

TODO: update `bh`-templates, update documentation 

/cc @mishanga @dfilatov @gela-d @sipayRT 
не по кодстайлу отсутствие пробелов в `{elem: 'clear'}`