I18n support for notifications

[Catizard]

This is a proposal for how we implement the i18n support for the in-game notifications:

• Reuse the UIResources.properties & ResourceBundle mechanism. This commit adds 3 messages for example, one is a simple welcome message, two are IR send success/failed messages.
• Introducing a simple structure to referencing the message key located at property files. See here. Although here's only one level, but it can be nested for more complex modules.

[Catizard]

I uploaded a change as a new proposal for error messages, which includes a way to automatically setup and print error code. Demanding further discussion.

[Catizard]

In most recent commit 0eb5b5f I filled several requirements from #159:

• There will be two log files: a user facing, and developer facing log file
• The developer log file must be in English
• stdout should be in the per-locale i18n format

Here's a small explanation of the implementation:

I added a class named I18nLoggerFactory as a replacement of LoggerFactory, which returns a proxied Logger instance called DuplexLogger, which delegates log invokes to one or two log backends on demand. More specifically, if the user's locale is english or hasn't been translated, there'll be only one logging backend (i.e. previous behavior without this pr). Otherwise, there'll be two logging backends: one is root(based on user's locale, output to console and beatoraja_log.xml), one is named as en(forced to use english locale, output to beatoraja_log_en.xml).

The actual translation is happened inside the class I18nLogger, which is a proxy of Logger again and simply translating the message upon the ResourceBundle it constructed with.

There's one drawback of this implementation: we need to replace all LoggerFactory.getLogger call with our own I18nLoggerFactory.getLogger. And may have a slight impact on logging efficiency.

[Catizard]

Update: error code mechanism is reimplemented. Marking this pr as ready for review because it is now demanding discussion around the designs. If there's no issues about the design I'll be going to process the migration.