Ui::MainWindow: Use TreeView instead of ListView
EditorController: Fix scale command call

Use multiplication instead of addition/subtraction to change the scale.
Add a digit to the scale display.
SvgAssembly: Add attribute hasChanged

Set it as false when saving/loading.
ViewController: Fix background creation

Avoid error message display when manipulating invalid path.
CompositorController: Add * to the tab name when the assembly has changed
SvgAssembliesList: Fix signals name

Add namespace in signals declaration.
Rename assemblyCreated to assemblyAdded
Add signal assemblyRemoved
SvgAssembly: Fix use of signal elementAdded

Always send the index.
TreeViewController: creation
TreeViewController: Implementation and use
test file change