Allow Akonadi resources to participate in online/offline mode switching

Currently kmail has only a hardcoded check for pop3 and imap resources
when switching online/offline mode.
That means new/3rd-party resources can not participate
in this switching.

With introducing a new capability label "NeedsNetwork"
in a resources .desktop file, kmail can now switch the online mode
for all resources which have this flag set.

REVIEW: 122228

kmkernel.cpp

@@ -932,7 +932,8 @@ void KMKernel::setAccountStatus(bool goOnline)
         const QString identifier( type.identifier() );
         if ( PimCommon::Util::isImapResource(identifier) ||
              identifier.contains( POP3_RESOURCE_IDENTIFIER ) ||
-             identifier.contains( QLatin1String("akonadi_maildispatcher_agent") ) ) {
+             identifier.contains( QLatin1String("akonadi_maildispatcher_agent") ) ||
+             type.type().capabilities().contains(QLatin1String("NeedsNetwork")) ) {
             type.setIsOnline( goOnline );
         }
     }