Fixes #1214 Language editor improvement

* editor finds translation issues and show appropriate info on files list when in editwith mode.
* editor finds translation issues and mark phrases that require attention when editing phrases in editwith mode.
* removed hardcoded html and added css classes to allow editor styling.
* improved stability.
* added support for RTL languages when editing (behavior can be controlled by CSS classes langeditor_rtl and langeditor_rtl in config_css)
* checked for various vulnerabilities
* fixes bug where in editwith mode, editor shows only variables that existed in both files but hides all other variables which caused unability to translate new variables.