Saving token for authentication
 - Instead of storing username/password onto pom or settings.xml
 - token will be stored in the user's home directory as .mvn-cf.xml
 - 2 new goals have been added. Login and Logout
 - Login goal will create the token file and also do the initial login
 - Logout will delete the token file and logout the user

Change-Id: Ifa13af764f107fa909d51381f906d5e83a262a64
Adding and supporting element <urls> to the configuration in pom.xml

 - Users can now have either <url> or <urls> inside their pom (They cannot have both at the same time).

 - The <url> and <urls> elements take effect during push and update goals.

 - Update goal has also been modified to support updating of memory, instances and uris.

Change-Id: Ide138e1d8f85fececbaac1c1651d943ee809f76d