Started implementing jar-based(plugin) tool loading

Core#plugin:
- Plugin.java: Main framework for plugins
- OllamaTool.java: Used for annotation based loading of tools
- InjectPlugin.java: Annoataion for injecting the Plugin instance, used when annotation based loading is used
- PluginMetadata.java: metadata of the plugin, a class-reflection of plugin.json file within each plugin
- PluginLoadingException.java: Exception thrown when an error happens durring plugin loading

Core/src/test/java/plugin/Test.java

@@ -0,0 +1,6 @@
+package plugin;
+
+import me.zacharias.chat.plugin.Plugin;
+
+public class Test extends Plugin {
+}