Documentation for new release features (#95)

* Split getMetaData method to allow being used in the stale sent messages
cleanup functionality
Better handling of errors in the cleanup method

* Optimise the getFileName methid
Add logging of ATTRIBUTES in trace log for debug purposes

* Fix resender functionality

* Allow modules to have scheduled tasks

* Add static for property defining how long before a pending file is
deemed stale

* Add scheduled task to track failed sent messages that have not been
cleaned up

* Add note regarding failed sent messages cleanup

* Scheduled tasks in modules allowed

* Add error message when stale file is removed

* Ensure inputstream is closed

* Handle quoted AS2 ID's when they contain a space character

* Helper method to remove double quotes

* Remove unused imports

* Fix the normalisation of AS2 ID from header.
Add Junit Test

* Change to accommodate byte array as response body instead of string

* Partnership classes and attribute statics rationalized and standardized

* Allow attributes in the partnership definition to reference other
attributes and replace at load time

* Fix null pointer exception

* Use HTTPEntoity to exgtract content and store as byte array instead of
string

* Add helper method to enhance attributes

* Update release notes to reflect the changes made in this commit.

* Update to release version number

* Document the items in the 2.5.0 release

* Fix release date

* Updated documentation for 2.5.0 release

* Documentation additions for 2.5.0