Encoding selection works
Disabled selecting in TreeView because of bugs.

Added some debug code.
Added base for loading files.

Only shows name in treeView, doesn't load to buffer.
Added selecting in treeView, again.

Doesn't update plainTextEditMain yet.
Finished loading and switching files.
Added asterisk to mark modified files.
Added saving current file.
Added encryption & buffer syncing on text change.

Flip bytes and rotating XOR algorithms only for now. Commented out the editingFinished() function.
Added tooltip to tree items, cleaned up ctor.

Moved properties initialization from addTreeItem to constructor.