Improve group layout demo.
We only need android api 18.
Update version number.
Rename Experiment to ExperimentData.

That matches the usage much besser and paves the way for an Experiment
class that performs an experiment.
Introduce a IExperiment interface and port the camera experiment to use it.

The idea is to have multiple experiments recorded in parallel using the
same ExperimentActivity. Is basically working for the camera experiment.
Store the whole script user data path when pausing.

This causes a crash when rotating the script activity. Fix the crashes
when failing to load the script so that only an error message is shown.