Cosmos: Provide facility to generate an aux collection

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At present, Equinox.Cli init will create a collection and add a stored proc. For the aux collection used by Change Feed Processors, adding the stored procedure should be made optional as this is step is not necessary for the Aux collection

See also #59 - in some cases users may not be interested in adding the stored procedure at the point of provisioning the collection in any case.

See also #61 - snapshots have different (no?) indexing requirements

We'll probably also make ./build provision an aux

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#65 implements the ability to skip provisioning the stored procedure

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#67 implements initAux as a hidden command (it presently does not set specific indices for backcompat purposes)