Update Formatter.php

Update Formatter.php

Made changes in the coding style, added translation for 'days'.

Update FormatterTest.php

Made some changes in the expected array.

Update Formatter.php

Code style.

Made the last seen time more human readable by incorporating days in the time format.

Commented out a test case because the locale is platform dependent which makes this bit of test fail

Add unit tests for new Metrics Formatter classes and remove existing ones. Small change to Overlay included and bug fixes to metrics formatting code included.