PERSONDIR-61: handle multi-valued attributes from Shibboleth SP

dixit https://wiki.shibboleth.net/confluence/display/SHIB2/NativeSPAttributeAccess:

	  multiple attribute values are separated by a semicolon,
	  and semicolons in values are escaped with a backslash.
This fails with an input string of "a;b\;". Results in
a
b\

Changing s to s2 results in what I believe is more appropriate behavior
a
b;

I will incorporate change and merge.