* Add Device to LocketTarget proto
* Refactor LockTarget.Match
* Test lib/srv.ComputeLockTargets
* Test lib/services.LockTargetsFromTLSIdentity
* Test device lock during cert issuance
* Add device lock targets where applicable
* Add --device to `tctl lock`
* Fix godocs (unrelated)
* Review: Drop redundant comments
* Add access request locks
This only contains the internal part, no user-visible changes
* Add a `tctl lock` flag to specify an access request ID
* Tests for access request locks
- Added ability to read AWS config from `~/.aws` directory for testing
- Fixed TTL bug in DynamoDB back-end
- Made FS back-end return similar error types as Boltdb does
- Cleaned up buggy tests for DynamoDB
- Removed unnecessary locks everywhere in code