feat: add support to observe scope vars to rerender bemjson
feat: add support to observe scope vars to rerender bemjson

`ngBemFactory`
  uses bemhtml from angular DI instead of ymodules one
  method `render` now only applies bemhtml transformations

`ngBemDirective`
  expects bemjson as angular expression in content or `bemjson` attribute
  bemjsonExpression can include references to current scope variables
  uses bemdom to replace directive element with rendered html
  saves context for later rerendering
  rerender occured on variable changes defined in `observe` attribute as comma-separated list

bem-contrib/ng-bem-components,bem-incubator/ng-bem-components,bem-incubator/ng-bem-components,bem-contrib/ng-bem-components,bem-contrib/ng-bem-components,bem-incubator/ng-bem-components