Extract EE specific files/lines for app/assets/javascripts/boards

We have the following files containing EE specific code. We should move them to ee/

• app/assets/javascripts/boards/components/modal/footer.js
• app/assets/javascripts/boards/components/sidebar/remove_issue.js
• app/assets/javascripts/boards/services/board_service.js
• app/assets/javascripts/boards/stores/boards_store.js
• app/assets/javascripts/boards/models/issue.js
• app/assets/javascripts/boards/models/list.js
• app/assets/javascripts/boards/index.js