Fixes #2392: Added `addCssStyle()`, `removeCssStyle()`, `cssStyleFromArray()` and `cssStyleToArray()` to `Html`

fixes yiisoft/yii#2844

issue #2043

A bit less stricter check as suggested by @qiang: https://github.com/yiisoft/yii2/commit/2aa8fc71714134feac3f0a09dd61837d920be534

Fixes #1610: `Html::activeCheckboxList()` and `Html::activeRadioList()` will submit an empty string if no checkbox/radio is selected

used e.g. for less client side compiling

"Item" parameter keys are the values of the checkbox list,
while the values are the checkbox labels.

added version, csrfVar and csrfToken to yii js module.