Merge upstream/master into chore/resource-server-consolidation

Brings in:
- #342 update dependency foundation to v6
- #349 bump parent v49 -> v50 (plexus-archiver CVE fix)

Conflict resolution: kept HEAD's deletion of
resource-server-content/src/main/webapp/rs/datatables/1.9.4/plugins/integration/foundation/index.html.
The entire rs/datatables/1.9.4/ directory is being removed in this
branch (see commit 85224df); upstream's #342 modification to that
file is irrelevant since the directory itself is doomed.

Author: bjagg

pom.xml

@@ -23,7 +23,7 @@
   <parent>
     <groupId>org.jasig.portlet</groupId>
     <artifactId>uportal-portlet-parent</artifactId>
-    <version>49</version>
+    <version>50</version>
   </parent>
 
   <modelVersion>4.0.0</modelVersion>