#697 - Clear all highlights every time items are set again, and refactor most things. Clear errors when linters are removed

test/test_linting_updates_loclist.vader

@@ -65,8 +65,4 @@ Execute(The loclist should be updated after linting is done):
   call ale#engine#WaitForJobs(2000)
 
   AssertEqual ['' . bufnr('%')], keys(g:ale_buffer_info)
-
-  let g:expected_data[0].match_id_list = [getmatches()[0].id]
-  let g:expected_data[1].match_id_list = [getmatches()[1].id]
-
   AssertEqual g:expected_data, g:ale_buffer_info[bufnr('%')].loclist