WIP: Vault End-Point Get/Head Update ** Needs Reviews before I can proceed**

CBDEUCE-89, CBDEUCE-111, CBDEUCE-112, CBDEUCE-113, CBDEUCE-114, CBDEUCE-115

DONE:
- Vault Head returns whether or not a Vault Exists
- Vault Get returns statistics on the vault
 - statistics are gathered from the drivers

Note: There are still several coverage issues in the drivers regarding how default values are returned.
deuce.drivers.cassandra.cassandrametadatadriver - lines 198-199
deuce.drivers.sqlite.sqlitemetadatadriver - lines 260-264
deuce.drivers.mongodb.mongodbmetadatadriver - lines 64,73, 82
deuce.drivers.swift.swiftstoragedriver - lines 86-87

Any suggestions on a good resolution welcome.

@TheSriram - not sure how that would work. Have an example?

(Yes, I'm aware of self.assertRaises...just not sure how it would work calling the internal function of a function of an object that relies on other aspects of the object...)

Essentially, to test these we might have to rely on mocking of the thing being queried, kind of like what I did for the Swift Driver where in the mock I enabled a special mode that simply and always threw the ClientException so as to be able to test those paths for the Swift Driver.