Limit number of ETags in header to e.g. 5

[Syndesi]

In the classes IfNoneMatchControllerEventListener and IfMatchControllerEventListener the client provided headers are read and parsed for ETags. Currently the number of possible ETags is unlimited / only restricted by HTTP limits.

Acceptance criteria:

• Limit number of ETags per requests to 5.
• Throw 400 bad exception (or better) should the user supply more than 5 ETags.
• Write feature test to verify this behavior.