Moved board store to namespaced gl object

app/assets/javascripts/boards/boards_bundle.js.es6

app/assets/javascripts/boards/components/board.js.es6

...ts/javascripts/boards/components/board_blank_state.js.es6

app/assets/javascripts/boards/components/board_card.js.es6

app/assets/javascripts/boards/components/board_list.js.es6

...ts/javascripts/boards/components/new_list_dropdown.js.es6

app/assets/javascripts/boards/models/issue.js.es6

app/assets/javascripts/boards/models/list.js.es6

app/assets/javascripts/boards/stores/boards_store.js.es6

app/assets/javascripts/labels_select.js

app/assets/javascripts/milestone_select.js

app/assets/javascripts/users_select.js

spec/javascripts/boards/boards_store_spec.js.es6

spec/javascripts/boards/issue_spec.js.es6

spec/javascripts/boards/list_spec.js.es6