show lang selector with locale's real name (in unicode)

e.g., now defaultly it will show 'English' in header, and show 'English', 'España', '简体中文', '繁体中文' in dropdown menu.

lang and its name mapping is defined in scripts/langMap.js, in the format
{
   lang_in_lowercase: unicode_name
}

if there can not find any mapping in langMap, the locale will be used.