Update openssl_signature module (#63)

* Use module_utils from collection, clean up code a bit

 * add DSA keys, because why not...

 * sign/verify was added in pyOpenSSL 0.11 apparently

 * Add signing capability detection to module_utils.crypto.basic

 * Rework feature detection of signature types.

 * Rename parameters to match other modules

 * Add initial version of integration tests

 * fix whitespace in tests

 * More whitespace fixes

 * small fixes for issues in testing

 * Organize integration tests as test matrix

 * another indentation fix to make pep8 happy

 * use openssl pkeyutl when possible, otherwise fall back to openssl dgst

 * More linter fixes

 * openssl pkeyutl -help can apparently return 1

 * ignore errors on openssl call and another try at formatting

 * Remove the OpenSSL calls in tests

 * Add collection name to deprecation notice and deprecate at version 2.0.0

 * Exclude Ed448/25519 tests on pyopenssl

 * revert the collection name in the deprecation notice (breaks 2.9)

 * limit test platforms even more

 * disable FreeBSD DSA and ECC tests

 * Add module name to README

 * rewrite and split into 2 modules instead

 * add module to README and fix whitespace issue

 * remove duplicated tests

 * address review remarks

 * resolve another comment

README.md

@@ -24,6 +24,8 @@ Most modules require a recent enough version of [the Python cryptography library
   - openssl_privatekey_info
   - openssl_privatekey
   - openssl_publickey
+  - openssl_signature_info
+  - openssl_signature
   - x509_certificate_info
   - x509_certificate
   - x509_crl_info