Remove GetCurrentSheet() from CalChartView

[rmpowell77]

These classes
class ContinuityBrowser;
class ContinuityBrowserPanel;
class PrintContinuityEditor;

are using these functions in CalChart View
auto GetSheets() const { return mShow->GetSheets(); }
auto GetCurrentSheet() const { return mShow->GetCurrentSheet(); }

We should look at alternatives so we can avoid returning the innards of the CalChart show and sheet privatives.

[rmpowell77]

Fixed with 573