Fix ClassCastException in AttributeSet (Fix #11286)

The helper getAttributeSortedStringSet fails loudly on
properties which are not strings. Instead we get each
object and do our best to convert it into a String.
Remove scifio from .classpath-template
Fix lenght typo
Merge pull request #2520 from joshmoore/11286-ldap-cce

11286 ldap cce