* Remove BouncyCastle dependency from runtime
This commit introduces a new gradle project that contains
the classes that have a dependency on BouncyCastle. For
the default distribution, It builds a jar from those and
in puts it in a subdirectory of lib
(/tools/security-cli) along with the BouncyCastle jars.
This directory is then passed in the
ES_ADDITIONAL_CLASSPATH_DIRECTORIES of the CLI tools
that use these classes.
BouncyCastle is removed as a runtime dependency (remains
as a compileOnly one) from x-pack core and x-pack security.