Organise Code

[rprospero]

Currently, the models, view, and demo executable are all dumped in a single folder. We should probably separate these.

This will require some care, since there are multiple ways of doing this split.

• Should the models go in one folder and the QML in another?
• Should there be one folder for each concept, combining the associated moel and view (e.g. LineModel.qml and lineGeometry.cpp)