[email] further improvements to test code and removal of emails validation

Changes list:

Email
---------------------
-Removed Email validation
-changed (back) to getInstance due to security exceptions caused when testing
using maven
-In setFrom(String email, String name) changed the checking to
StringUtils.isNotEmpty
-Fixed some incorrect logic in testing for charset in:
addTo(String email, String name)
addCc(String email, String name)
addBcc(String email, String name)
addReplyTo(String email, String name)

Mulitpart Email
---------------------
-Corrected style errors involving imports
-Added validation to disallow null message contents in setMsg(String msg)
-Removed redundant if statment from send() to streamline the function
-Added validation to disallow null attachements to attach(EmailAttachment
attachment)
-Added URL validation for attach(URL url, String name, String description,
String disposition)
-Added Datasource validation for attach( DataSource ds, String name, String
description)
-Removed redundant if statement from getPrimaryBodyPart() as the code was a
duplicate of code inside init()

EmailAttachmentTest
---------------------
-Coding style changes only

EmailTest
---------------------
-Added test for the Get/Set session
-Minor Coding style changes
-Added exception test for the person param to all relevant address functions
-Added the server port as a configurable var and added it as a static property
-Added code to set the configured port during tests

HtmlEmailTest
---------------------
-Minor Coding style changes
-Added the server port as a configurable var and added it as a static property
-Added code to set the configured port during tests

MulitpartEmailTest
---------------------
-Minor Coding style changes
-Added the server port as a configurable var and added it as a static property
-Added code to set the configured port during tests
-Removed the hard coded test url and added reference to the configuration
class instead
-Added test for init

SimpleEmailTest
---------------------
-added apache license
-Minor Coding style changes
-Added the server port as a configurable var and added it as a static property
-Added code to set the configured port during tests

EmailConfiguration
---------------------
-added apache license
-Minor Coding style changes
-changed the test url to a active url

MockEmailConcrete
---------------------
-added apache license
-Minor Coding style changes
-added function to help test get/set session

MockHtmlEmailConcrete
---------------------
-added apache license

MockMulitPartEmailConcrete
---------------------
-added apache license
-added test for init function

MockHtmlEmailConcrete
---------------------
-added apache license