Removing reduant X-Client-App-Id and X-Client-App-Key headers.

[MurashovVen]

Now, X-Client-App-Id and X-Client-App-Key are redundant after merging PR 66.
We can decide what we gonna do with it.

[MurashovVen]

Also, this feature was mentioned there.

[stewartie4]

I agree, the signature identifies the user now.
The only case I can think of is the consumer of an auth ticket - is a signature used in those cases too?
If so then I don't see what purpose these serve now

[stewartie4]

The X-Client-App-Id header itself may still be needed in order to identify collaborators, especially if collaborator support is added to the endpoints listed in #66
The presence and owner checks on the contents of this header are redundant though as is the X-Client-App-Key header