Change NameFormat to BEM

This is so that variables like `$component__variable-name` can work. Previous rule (hyphenated_lowercase) would throw a warning on that variable name.

Status: **Opened for visibility**
Reviewers: @kpeatt @ry5n 
JIRA: **n/a**

## Changes
- Changed `NameFormat` from `hyphenated_lowercase` to `BEM`