[select]: added passing tabindex to button block

Fixes #1174
[select]: specs for tabindex
Merge pull request #1175 from zxqfox/feature/select-tabindex

added passing tabindex to button block
[image] div => span in tmpl-specs

Fixes #1192
[select] fixup tabindex tests according to button aria-hidden
Merge pull request #1193 from zxqfox/hotfix/image-tests

Hotfix/image tests
[link] add sizes for islands theme

Fixes #1182
add link to islands page with all 4 sizes
change link size in showcase to large
[link] add _size to docs
Merge pull request #1195 from zxqfox/feature/link-size-modifier

link: add sizes for islands theme
add block 'form'
add 'form__input' element
add 'form__input_type' modifier
add 'form__input_type_input' modifier
getVal and setVal instead val
add form__input_type_checkbox modifier
move event handlers to form__input_type modifiers
refactor form__input_type_input bemhtml template
add element form__input to deps
rename form__input to form__control
add form__control_type_radio modifier
use boolean modifiers instead yes values