Mapping of lefthand nav objects to page object

Changes in this PR* filtered "map to this object" link to only show up if the two types can be mapped.* Each primary object class has a "links_to" property that determines what can be mapped and how (join class or Relationship)* "map" button in extended info div hooked up to functionality* if the type of join is a Relationship, pops up a modal asking the user to choose the relationship type.* only fully supported for Program page, currently.