m_spanningtree Throw an exception on protocol violations instead of returning CMD_INVALID

Catch CoreExceptions, log and close the link in OnDataReady()
m_spanningtree Add ServerCommand::ExtractTS() to convert string to raw TS

Throws a ProtocolException if the input is invalid
Change the OnNamesListItem() hook to return ModResult

Return MOD_RES_DENY to exclude a user from a NAMES list
Document parameters and return value for the OnNamesListItem hook