for config.get callbacks, pass closures

The essence of this change updates plugins that pass a callback to config.get() to pass a closure instead of a function reference. In most cases, callbacks are being passed that save the config settings to plugin.cfg. To make testing easier, those anonymous functions with closures are now stored on exports.

* Resolves Issue #784. Everywhere. I think.
* update tests due to some function renames (ex: load_config -> load_[plugin.name]_ini)
* adds a few tests.