Allow for loading of experiments after they have finished.

[szmoore]

Currently there is no way to recover data from a previous experiment. This should be fixed.

Currently Data_Open will open a new data file (or overwrite an existing one) for a particular sensor/actuator.

Suggest implementing a flag or alternative function to open an existing file. The same server API can then be used to review data from previous experiments.

Consider whether the user should be able to append data to a loaded experiment (would require updating the timestamps relative to the actual start time of the experiment, rather than the time at which it was loaded) or only allow viewing (ie: do not start sensors recording data, disallow actuators being set).

[szmoore]

This is similar to "Add ability to list and view past experiments" but focuses only on the changes to the server, not the enhancements needed in the GUI.