LPS-50081 move attachment code into parent class

Move all common code related to attachments into parent class.
LPS-50081 move common subscription logic into parent
LPS-50081 move RSS logic into parent class

While AdminPortlet doesn't support RSS, I'm pushing RSS functionality up
into the parent class to remove duplication in the other portlets.
LPS-50081 move common KBComment code into parent class
LPS-50081 move error exn checking into parent class
LPS-50081 move delete & move logic into parent
LPS-50081 extract edit URL logic into its own method
LPS-50081 move updateKBArticle to parent
LPS-50081 move serveResource into parent class
LPS-50081 move checkExceededSizeLimit into parent
LPS-50081 rename kbComment status parameter

The param name "status" is used both for the article and comment
status. Rename the comment parameter to kbCommentStatus to avoid
conflict.
LPS-50081 Include back missing exception
LPS-50081 Make it final and order it
LPS-50081 remove hardcoded portlet id
LPS-50081 move common code into parent class
LPS-50081 Use portletDisplay
LPS-50081 SF