Copy service code from abandoned DS-1182 attempt.
Clean up unused imports
Get tests to run
Add configuration setting to name the mail Session object to be sought from JNDI
Make DSpace actually use EmailService
Remove imports no longer used
Add some imports lost in conflict resolution after rebasing
Fix service initialization and behaviour when authentication is required
Merge pull request #210 from mwoodiupui/DS-1269

[DS-1269] EmailService to encapsulate the sending of mail