Switch to sslcrypto for cryptography tasks (#2338)

* Use sslcrypto instead of pyelliptic and pybitcointools

* Fix CryptMessage

* Support Python 3.4

* Fix user creation

* Get rid of pyelliptic and pybitcointools

* Fix typo

* Delete test file

* Add sslcrypto to tree

* Update sslcrypto

* Add pyaes to src/lib

* Fix typo in tests

* Update sslcrypto version

* Use privatekey_bin instead of privatekey for bytes objects

* Fix sslcrypto

* Fix Benchmark plugin

* Don't calculate the same thing twice

* Only import sslcrypto once

* Handle fallback sslcrypto implementation during tests

* Fix sslcrypto fallback implementation selection

src/lib/sslcrypto/LICENSE

@@ -0,0 +1,27 @@
+MIT License
+
+Copyright (c) 2019 Ivan Machugovskiy
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+
+
+Additionally, the following licenses must be preserved:
+
+- ripemd implementation is licensed under BSD-3 by Markus Friedl, see `_ripemd.py`;
+- jacobian curve implementation is dual-licensed under MIT or public domain license, see `_jacobian.py`.