Array#to_sentence(:locale => Asia) improvement

Similar to #1294 Add word separator for AR error messages

Array#to_sentence method cannot properly handle the corresponding expression in Eastern languages which don't use those characters (like Japanese, Chinese, etc).

Problem here again, is that comma and space character are hardcoded inside the "I18n ready" source code.

This patch moves these "Western" characrers into the locale resource file, without changing the default en-US behavior.

This enables Array#to_sentence to generate a natural spoken Japanese with the following locale settings.

ja-JP:
  support:
    array:
      words_connector: "と"
      two_words_connector: "と"
      last_word_connector: "と"