add module alias '@tests/'

Alias would remove unnecessary repetitions and less relative paths make changes easier when moving around files. This commit cleans also up some relative paths ('../../../') by using the alias and orders imports. It updates both path alias in tsconfig and module alias in Vue CLI's bundler (vuejs/vue-cli#2398).

src/application/collections/collection.yaml.d.ts

@@ -1,4 +1,4 @@
-declare module 'js-yaml-loader!*' {
+declare module 'js-yaml-loader!@/*' {
     export interface CollectionData {
         readonly os: string;
         readonly scripting: ScriptingDefinitionData;