Updated plugin callback demo
Updated plugin tester
Merge branch 'adding_plugin_documentation' of https://github.com/TotteKarlsson/roadrunner into adding_plugin_documentation
Added firstNextPrevious plugin API functions
Added assignRRHandle ToPlugin API function

Cleaned up C plugin class
Made Plugins friend to PluginManager
Merge branch 'develop' into adding_plugin_documentation
Merge branch 'adding_plugin_documentation' into more_docs_dec4
Merge branch 'adding_FirstNextPrevPlugin_api_functions' into more_docs_dec4
Added simple app to use C API

Added C docs