request and response. This makes it far easier to properly check
validity elsewhere in Vault because we simply replace the request client
token with the inner value.
This commit splits ACL policies into more fine-grained capabilities.
This both drastically simplifies the checking code and makes it possible
to support needed workflows that are not possible with the previous
method. It is backwards compatible; policies containing a "policy"
string are simply converted to a set of capabilities matching previous
behavior.
Fixes#724 (and others).
