feat: isolate scope in `iBemDirective`, expose `$bem` object to it
feat: isolate scope in `iBemDirective`, expose `$bem` object to it

it will simplify access to i-bem blocks in other directives like `ng-click`

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