* website: add note about the 0.9.2+ CLI changes to reduce confusion

* website: fix frontmatter for 0.9.3 guide, add to guides index

* website: add overview title to 0.9.3 guide for spacing

Fixes #3858

* Remove logical.Initialize() method

* More cleanup

* Fix test

* auth/aws: Fix error with empty bound_iam_principal_arn

In cases where there doesn't need to be a bound_iam_principal_arn, i.e.,
either auth_type is ec2 or there are other bindings with the iam
auth_type, but it is specified explicitly anyway, Vault tried to parse
it to resolve to internal unique IDs. This now checks to ensure that
bound_iam_principal_arn is non-empty before attempting to resolve it.

Fixes #3837

* Fix extraneous newline

* Fix intermittent panic by storing a reference to the grpc server and
using that to ensure it will never be nil.

* Just get rid of c.rpcServer

* Use version to determine plugin protocol to use

* Remove field from ServeOpts

* Fix missing assignment, handle errors

* contraint -> constraint

* Inject the version string from the vault side

* Fix the version check

* Add grpc support check to database plugins

* Default to use grpc unless missing env var or fail on contraint check

* Add GRPCSupport test

* Add greater than test case

* Add go-version dep

Fixes #2030

* Update data values from byte arrays to strings in proto definition

* Update comments