Upgrade Vue from 2.6.12 to 2.7.16 (#2489)

Also upgrade unit test dependencies and unit test and and ESLint config 

See https://v2.vuejs.org/v2/guide/migration-vue-2-7 for Vue migration guide.
See https://github.com/vuejs/vue-test-utils/ and https://github.com/vuejs/vue-jest for unit tests.
See https://github.com/vuejs/eslint-plugin-vue/releases/tag/v9.0.0 for ESLint rule changes.

Signed-off-by: Florian Hotze <florianh_dev@icloud.com>

bundles/org.openhab.ui/web/.eslintrc.js

@@ -69,13 +69,15 @@ module.exports = {
     'vue/attribute-hyphenation': 'off',
     'vue/attributes-order': 'off',
     'vue/component-definition-name-casing': 'off',
+    'vue/first-attribute-linebreak': 'off',
     'vue/html-closing-bracket-newline': ['error', { 'singleline': 'never', 'multiline': 'never' }],
     'vue/html-closing-bracket-spacing': 'error',
     'vue/html-indent': 'error',
     'vue/html-quotes': 'error',
     'vue/html-self-closing': 'error',
     'vue/max-attributes-per-line': 'off',
     'vue/multiline-html-element-content-newline': 'error',
+    'vue/multi-word-component-names': 'off',
     'vue/mustache-interpolation-spacing': 'error',
     'vue/no-multi-spaces': 'error',
     'vue/no-v-html': 'off',

bundles/org.openhab.ui/web/jest.config.js

@@ -2,6 +2,7 @@ module.exports = {
   globals: {
     __DEV__: true
   },
+  testEnvironment: 'jest-environment-jsdom',
   // setupFilesAfterEnv: [
   //   '<rootDir>/test/jest/jest.setup.js'
   // ],
@@ -50,7 +51,7 @@ module.exports = {
     // '.*css$': '<rootDir>/test/jest/utils/stub.css'
   },
   transform: {
-    '.*\\.(vue)$': '<rootDir>/node_modules/vue-jest',
+    '.*\\.(vue)$': '@vue/vue2-jest',
     '.*\\.js$': 'babel-jest',
     '.+\\.(css|styl|less|sass|scss|svg|png|jpg|ttf|woff|woff2)$': 'jest-transform-stub',
     '^.+\\.nearley$': 'jest-transform-nearley'