Add the intial character retrieve method.

Retrieve the unique initial characters of all entries in the entry table
sorted by character.
Add the initial char template part.
Update the Manage page to use the init char template part.
Update the cnRetrieve::getCharacters method to use the new query parts for the WHERE SQL clause.
Add default atts to cnTemplate::character().
Pass the entry status page tab to the cnTemplate::character() method.
Add setQueryStatus & setQueryVisibility to cnRetrieve. These query parts are used to set the WHERE SQL clause.