Consolidate linguist examples

The examples in Qt Linguist should be revised & consolidated. In particular, they do not follow best practices:

• All of them look up the translation files in the current working directory, which is confusing especially for shadow builds. Instead, the qrc system should be used (possible nowadays with CONFIG += lrelease embed_translations)
• The current locale is determined via QLocale::system().name(). Instead, best practice is to use QTranslator::load(QLocale(), ...).

Qt Linguist Examples

• Arrow Pad Example
• Hello tr() Example
• Troll Print Example

There are also other examples and demos that do show translation support:

• I18N Example
• Qt Quick Demo - Photo Viewer
• Hello Script Example

Finally, some examples do contain QTranslator setups that do not follow best practices, either:

• Standard Dialogs Example
• Class Wizard Example
• Trivial Wizard Example