Adds progress to find all references

Progress is added via the status bar.  This was done via making a unified API with the FSharp.ViewModule ProgressManager, so the same code can report to either (or both) locations.

In addition, improves rename to match, so it reports progress to status bar as well as dialog.

Addresses Issue #516

Also: Fixes dialog height for comment in #511

We use `x` for object identifier. More information on code styles is available in https://github.com/fsprojects/VisualFSharpPowerTools/blob/master/CONTRIBUTING.md#code-styles.