* govet cleanup in token store
* adding general ttl handling to login requests
* consolidating TTL calculation to system view
* deprecate LeaseExtend
* deprecate LeaseExtend
* set the increment to the correct value
* move calculateTTL out of SystemView
* remove unused value
* add back clearing of lease id
* implement core ttl in some backends
* removing increment and issue time from lease options
* adding ttl tests, fixing some compile issue
* adding ttl tests
* fixing some explicit max TTL logic
* fixing up some tests
* removing unneeded test
* off by one errors...
* adding back some logic for bc
* adding period to return on renewal
* tweaking max ttl capping slightly
* use the appropriate precision for ttl calculation
* deprecate proto fields instead of delete
* addressing feedback
* moving TTL handling for backends to core
* mongo is a secret backend not auth
* adding estimated ttl for backends that also manage the expiration time
* set the estimate values before calling the renew request
* moving calculate TTL to framework, revert removal of increment and issue time from logical
* minor edits
* addressing feedback
* address more feedback
* Start work on passing context to backends
* More work on passing context
* Unindent logical system
* Unindent token store
* Unindent passthrough
* Unindent cubbyhole
* Fix tests
* use requestContext in rollback and expiration managers
1) Use the new LeaseExtend
2) Use default values controlled by mount tuning/system defaults instead
of a random hard coded value
3) Remove grace periods
