i18n fixes (#1614)

* i18n fixes

- fix issue with default (fallback) language set to browser language
- fix issue with fallback language loading when browser language set to
non-English locale

* code and UI fixes

- move document list i18n strings into own scope
- replace MDL menu with @angular/material menu (fixes issue with menu
items translation, not supported by MDL)
- minor improvements

* fix unit tests

* improve i18n docs and code

- provide basic documentation for Translation service
- remove custom Login component localisation in favour of documentation
sample
- simplified i18n setup for demo shell (single path for dev/prod env)

* remove unnecessary comments

demo-shell-ng2/config/webpack.prod.js

@@ -66,9 +66,9 @@ module.exports = webpackMerge(commonConfig, {
             to: 'pdf.worker.js'
         },
         {
-            context: 'custom-translation',
+            context: 'resources/i18n',
             from: '**/*.json',
-            to: 'i18n/custom-translation'
+            to: 'resources/i18n'
         },
         // Copy i18n folders for all modules with ng2-alfresco- prefix
         {