Add SHA256 hashing code

Needed for #108

CMakeLists.txt

@@ -130,6 +130,7 @@ target_include_directories(teqpinterface INTERFACE "${CMAKE_CURRENT_SOURCE_DIR}/
 target_include_directories(teqpinterface INTERFACE "${CMAKE_CURRENT_SOURCE_DIR}/externals/nlohmann_json")
 target_include_directories(teqpinterface INTERFACE "${CMAKE_CURRENT_SOURCE_DIR}/boost_teqp")
 target_include_directories(teqpinterface INTERFACE "${CMAKE_CURRENT_SOURCE_DIR}/externals/REFPROP-interop/include")
+target_include_directories(teqpinterface INTERFACE "${CMAKE_CURRENT_SOURCE_DIR}/externals/stbrumme-hashing/include")
 
 if (NOT TEQP_NO_TESTS)
   add_subdirectory("${CMAKE_CURRENT_SOURCE_DIR}/externals/Catch2")

externals/stbrumme-hashing/LICENSE

@@ -0,0 +1,10 @@
+zlib License
+
+Copyright (c) 2014,2015 Stephan Brumme
+
+This software is provided 'as-is', without any express or implied warranty. In no event will the authors be held liable for any damages arising from the use of this software.
+Permission is granted to anyone to use this software for any purpose, including commercial applications, and to alter it and redistribute it freely, subject to the following restrictions:
+1. The origin of this software must not be misrepresented; you must not claim that you wrote the original software.
+   If you use this software in a product, an acknowledgment in the product documentation would be appreciated but is not required.
+2. Altered source versions must be plainly marked as such, and must not be misrepresented as being the original software.
+3. This notice may not be removed or altered from any source distribution.