Moved plugins and add loaded file filtering

- Moved prettify_json and lsp_completer plugins to sub categories
- Add filter_out_loaded_files to prevent opening already-loaded files
- Refactor code events into single events module
- Fix signal blocking during file load operations
- Include READONLY state in source view lifecycle handling

plugins/code/event-watchers/prettify_json/manifest.json

@@ -0,0 +1,7 @@
+{
+    "name": "Prettify JSON",
+    "author": "ITDominator",
+    "version": "0.0.1",
+    "support": "",
+    "requests": {}
+}