* Moved Setter next to Getter
* Set `config_dir` to ensure consistent directory for all files resolving #2551
* Changed PluginManager loading log message to include directory
* Rework Plugin Manager so that plugins can be loaded after initialization
* Use a callback function to add plugin tabs to the dialog
* Install button lets you choose plugin file, copies it to plugins directory, and immediately loads it
* Remove button deletes selected plugin file from plugins directory - need to add a means to unload it first