Add Sakai Connector Portlet and Basic LTI Portlet to uPortal

The Sakai Connector and Basic LTI portlets have fulfilled all requirements for Jasig incubation. 

Both portlets are deployed to Maven Central and are deployable via the standard uPortal ant deployPortletApp command.

I have created portlet overlays for both portlets and included default configuration so that each portlet is setup with a demo.

This pull request adds both to the uPortal codebase.

Incubation Jiras:
Sakai Connector https://issues.jasig.org/browse/INC-23
Basic LTI Portlet https://issues.jasig.org/browse/INC-40