Refactor Composer

- Have a simple HTextArea component instead of HScrollTextArea
- Split composer parts between multiple files

TODO.md

@@ -7,12 +7,12 @@
   - Use new default/reset controls system 
   - Display name field text should be colored 
 
-- Split `HScrollableTextArea` into `HTextArea` and `HScrollView` components
-- Refactor `Composer`
-
 - Drop the `HBox` `buttonModel`/`buttonCallbacks` `HBox` approach,
   be more declarative
 
+- Reorder QML object declarations,
+  conform to https://doc-snapshots.qt.io/qt5-dev/qml-codingconventions.html
+
 ## Issues
 
 - SSL error on python 3.7