Makes ContentFormat modifiable

[WilliamBruneau]

ContentFormat used to be hardcoded as "RenderedText". This means that all subscriptions retrieved RenderingInfo of all events.

RenderingInfo can be useful for event analysis but it increases event size. It seems necessary to make it configurable.

With this PR, ContentFormat is configurable and can have 2 values: "RenderedText" or "Raw".

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

This option determines how the event data will be received by the event subscriber. If the
value of this option is "RenderedText", both the event data and rendering information are
passed, whereas event data is contained within the element and rendering
info is contained with the element , so that the event can be displayed by
the event subscriber according to a predefined format. The default value for this option is
"Raw", which means that only event data will be passed without any rendering information.