core: Underscores in tag names break tags

Problem were in the usage of the deprecated RefObject objects to pass
strings in *AutoCompleter* classes .
This was replaced with a native String usage

The signature and calls to formatValue had changed to get a
Pair<String,String> instead of two Strings encapsulated by a RefObject.

Change-Id: I8c0d48aa8ab693149fd1dcc080eddd6d2f9ba4ed
Bug-Url : https://bugzilla.redhat.com/show_bug.cgi?id=949484
Signed-off-by: Eli Mesika <emesika@redhat.com>