Added composer installed PEAR mimeDecode  to decode email headers

There can be chances of the recieved email being encoded, headers
wrapped, lowercased or misplaced. Including a class for handling
would save a lot of regex work.
The library can be installed by composer install

Change-Id: I6de9f788d6105097ff5e6b343f5ce29548f53798
Merge "Added composer installed PEAR mimeDecode  to decode email headers"