LPS-45403 Add URL title to KBArticle - Part I

Hi Peter,

This change adds URL title as an attribute of the kb article entity and its services. On importing Dev Site articles, we'll specify URL titles for each article. The logic in the LSI assures they are unique. This logic is also used in JournalArticle LSI.

In Part II of my changes, I'll send you the friendly URL mappings and JSP modifications to alternatively display the articles by URL title.

If you could review these changes I'd appreciate it. If you're tied up with other things, just respond to this PR and Sergio can find a collab team member (or he himself) to review. Thanks.

@sergiogonzalez @jorgeferrer