ecere/i18n; ide: Improved adapting to LANGUAGE env. variable

ecere/i18n; ide: Improved adapting to LANGUAGE env. variable
- i18n: Fixed a bug preventing genericLocale to work on app executable
- Understanding generic 'zh' as 'zh_CN'
- Saving IDE settings language value on startup
- Handling LANGUAGE value with multiple locales separating by : (only first is looked at for now)
- Applying same logic to checked language menu items as translation loading code (generic locales to use e.g. en for en_CA)
- Ensuring an item is checked (default to english if no locale is found)