issue #45: added control from eac; added fileDesc to it
fileDesc/titleStmt author and fileDesc/titleStmt now zeroOrMore
created controlNote; languageDeclarations

languageDeclarations wraps languageDeclaration and is available as
choice between languageDeclaration and languageDeclarations
minor changes
issue #45: added "unknown" as value of maintenanceHistory/@eventType and @agentType

to faciiitate migration from EAD 2002
fixed content model of languageDeclartions

one require languageDeclaration and then oneOrMore languageDeclaration
added valid control
fixed reference and definition of controlNote
minor changes