Add IgnoreChannelError option to subscriptions

[vruello]

The Ignore Channel Error option allows you to decide whether a client should continue processing a subscription if an error occurs within its channel filters :

• true: the error is ignored (default)
• false: the processing stops if an error occurs

Prior to this update, this option was hardcoded to true.

See documentation for more details: [MS-WSMV] 3.1.4.1.30.1 Subscription Options :

This option determines if various filtering options resulting in errors in different channels
are to result in termination of the processing. It has the xsi:nil attribute associated with it, 
whose value is set to "true", meaning that the filtering errors in different channels MUST be
ignored by the subscription service and processing SHOULD continue.