(PE-5502) Support for loading chained certificates into a KeyStore

This commit adds support for loading a chain of certificates into the
same entry in a KeyStore.  This includes the following changes:

* An overload of the associatePrivateKey() method on the
  CertificateAuthority Java class was introduced to enable passing in
  multiple certificates to be stored in the KeyStore entry.

* All of the certificates found in a Reader passed into a call
  to associatePrivateKeyFromReader() will be used in the certificate
  chain stored in the KeyStore entry.  Previously, if more than 1
  certificate was found in the Reader, an `IllegalArgumentException` was
  thrown.
I'd gone with `List` here because I had some code I was using to build up the argument I pass into this which uses Java's `ArrayList`.  The `coll?` and `list?` Clojure functions would both return false for a Java `ArrayList`.  A Clojure vector, Clojure list, or Java `ArrayList`, though, would return 'true' for `(instance? List)`, so I thought this might be *more* usable than just `coll?` or `list?`.  Probably some cases I'm missing?