Clean up the plugin-host interface
Start fixing up code to match coding standard

Adhere to convention in include/plugin_i.h

Adhere to convention for filenames: function.{cpp,hpp}

Adhere to convention for filenames: invoker.{cpp,hpp}

Adhere to convention for filenames: plugin.{cpp,hpp}

Adhere to convention for filenames: plugin_description.{cpp,hpp}

Adhere to convention for filenames: plugin_library.{cpp,hpp}

Remove util.h

Adhere to convention for filenames: plugin_manager.{cpp,hpp}

Adhere to coding standard: do not use std::

Adhere to coding standards for lower case class names

Rename Invoker to invoker

Renamed Plugin to plugin

Rename PluginDescription

Rename PluginLibrary

Rename PluginManager