Adding new PluginExecutor command

Resolves #101

- A plugin class can be defined outside of the Adam jar, but run through
  the normal AdamMain
- An example plugin, the "Take10Plugin" is included in the test
  directory
- Adds a test suite to the cli module, which can reference the items
  available in the core module
- Adds notion of AccessControl to control the records which can be
  accessed