The command tool's cache is serialized with the BinaryFormatter

[teo-tsirpanis]

As seen in BuildCommand.fs, the project cracker cache the command tool stores in .fsdocs/cache is serialized using the insecure and deprecated BinaryFormatter class.

To close this potential security hole, the command tool should use a safe serializer for its cache, such as the data contract serializer. Such change would break the existing cache files but the impact from this change is minimal.