Make sure we merge users when performing imports.

Previously importing of users was disabled. This re-enables it so that users who were previously in a site are in it again.
Actually add the members to the imported site.

Previously we just imported the people and the site but didn't make them members of the site. This change and the previous change should be deployed with changes to the kernel which improve the merging of users
when they are provided.
Conflicts:
	archive-impl/impl2/src/java/org/sakaiproject/archive/impl/SiteMerger.java
WL-1016 Added IMS CP handling to 'import from file'
WL-1269 IMS CP import: display >1 item in picker.
If there's only 1 item at the top level, look for child items instead.
WL-1283 Fixed XPath for reading item description.

Conflicts:
	import-impl/src/java/org/sakaiproject/importer/impl/IMSFileParser.java
WL-1292 Stop auto-unpacking of imported zip files