GEODE-2607: improve release artifacts

- Add packer and docker directories back into release artifacts 
  Geode leaves these in, so it's best to match what they do when we can.

- Generate SHA512 has along with build artifacts.

Co-authored-by: Ivan Godwin <igodwin@pivotal.io>
diff --git a/.cpackignore b/.cpackignore
index 8f18540..5b3f03d 100644
--- a/.cpackignore
+++ b/.cpackignore
@@ -1,5 +1,3 @@
-/docker/
-/packer/
 /.git/
 /.DS_Store
 
diff --git a/CMakeLists.txt b/CMakeLists.txt
index bbb5869..c7c7e54 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -110,6 +110,7 @@
 set(CPACK_RESOURCE_FILE_LICENSE "${CMAKE_CURRENT_SOURCE_DIR}/dist/LICENSE")
 set(CPACK_PACKAGE_INSTALL_DIRECTORY "${CPACK_PACKAGE_NAME}")
 set(CPACK_GENERATOR TGZ;ZIP)
+set(CPACK_PACKAGE_CHECKSUM "SHA512")
 
 # Build a comprehensive list of things to leave out of the cpack package for our
 # source code releases.  Use .gitignore as a base, then use '.cpackignore' to