* added signature field -- no function yet
* added mail signature feature
* fixed style issue
* fixed problem with signature default
* added unit test for mail signatures
* added unit test for mail signatures
* add ajax and dummy api response
* add preview <p> blocks
* finalise order_placed setup
- use <pre> for mail preview
- create dummy data in backend
* fix i18n text conversion
* create fragment template for mail preview
* support i18n in mail preview view
* apply mail fragment in all mail settings
fix mistake in input[lang=en] flag style
add dummy data for all placeholders
apply fragment template to all fields
add exclude option to fragment template
* remove migration file
* add translation mapping & fix field label
remove hardcoded field label
add transblock for translation file
* add test for mail setting preview
* fix code style in preview class
* bug fix in mail preview view
- fixed localised date values
- added locale index mapping
- added tests on multi-language event
- enhanced dummy data
