Allow for conscious decisions to re-establish limits

[HorridTom]

In some scenarios it can be advantageous to only re-establish limits if i) there is a new process and ii) the analyst or team agree that new limits should be established.

For example, if it is imperative that a measure returns to within existing limits, the team may prefer not to re-establish limits and instead to work hard on the process to bring it back into statistical control against the original limits. This may be useful if for example re-establishing limits could be seen as somehow legitimising a new, inferior, process.

It would therefore be useful to allow users of the algorithm to review and approve re-establishment at each point the algorithm identifies as a re-establishment point.

There are several factors to consider in designing a feature or features to address this:

1. How should the decision "data" be provided to the algorithm. This could be a) through some sort of argument passed to plot_auto_SPC (or a new plotting function), b) through a column in the data or c) through an interactive prompt
2. Ignoring a re-establishment may impact on the validity of the algorithm's subsequent analysis - e.g. a shifted process may continue to trigger the algorithm - should the user be prompted / have to approve every time?
3. How should the fact that re-establishment has been suppressed be indicated on the chart? It should be, to ensure the method used for resulting analyses is clear.

This issue will therefore require some careful thought and design prior to implementation.