(TK-121) Added CRL support to SSLContext creation functions

This commit contains the following additions:

* Adds an overload of the `pems->ssl-context` Clojure function and
  `pemsToSSLContext` Java method which accept an argument coerceable
  into a CRL file `Reader`.  The `Reader` is used to pull out any
  CRL PEMs and apply those to the `SSLContext`.  A client using the
  new `SSLContext` would have certificate revocation checking against
  the CRLs performed during the creation of new context sessions.

* Adds a `pem->crls` Clojure function and `pemToCRLs` Java method for
  converting a PEM with multiple CRLs into a "collection" of `X509CRL`
  objects.
(TK-121) Added CRL option to ca-cert only SSLContext

This commit adds the ability to include the CRL when creating an
SSLContext from a CA pem only, i.e., without a private key and
client/server certificate.  A `ca-cert-and-crl-pems->ssl-context`
Clojure function and `caCertAndCrlPemsToSSLContext` Java method were
introduced to support this.

This commit also includes a bit of refactoring intended to DRY up the
code a bit more and avoid including new exceptions related to CRL
handling on the throws clause for existing Java methods that don't take
a CRL argument.
(TK-121) Added sentence about `crls` to function docstring

This commit adds a sentence about the `crls` parameter in the
`ca-cert-and-crl-pems->ssl-context` function to the function's
docstring.
Merge pull request #42 from camlow325/maint/master/TK-121-add-crls-to-ssl-context

(TK-121) Added CRL support to SSLContext creation functions