textarea: Create as separate block

Close #1033
I've made only basics yet: `common`+`desktop`, `BEMHTML`-templates, js, styles only for `islands` theme.
I didn't remove `input_type_textarea` to have ability to compare new block with it.
Взято из input_type_textarea - https://github.com/bem/bem-components/blob/v2/design/common.blocks/input/_theme/input_theme_islands.styl#L276

Может @gela-d подскажет?