Added code level documentation to the PluginService
Merge pull request #73 from pencilblue/story/PLUGIN_FRAMEWORK_DOCUMENTATION

Added code level documentation to the PluginService
Fixes #74.  Provides a mechanism for processes to communicate back and forth.
Merge pull request #75 from pencilblue/story/PB74

Fixes #74.  Provides a mechanism for processes to communicate back and forth
#74 Initial concept for allowing plugins to have dependencies.
#46 Implements plugin dependencies
Merge pull request #77 from pencilblue/story/PB46

Fixes #46
Merge branch 'master' into wp_import