feat(sort): add a Clear Sorting function and grid menu command

[ghiscoding]

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[ghiscoding]

@jmzagorski
Another PR if you have time to review, or I can merge it and release on Monday/Tuesday. Not a problem if you can't review, I know you're quite busy :)

[ghiscoding]

@jmzagorski
FYI and in case you haven't noticed, I'm starting to simplify each Services init() function (or whatever function name is used for initializing the service). I don't want to do these changes all in 1 shot, so I do them when I touch them and test them. Basically, what I started to do is eliminate gridOptions and columnDefinitions and keep only grid and dataView objects.

Why the refactoring?
Because it's much simpler to deal with only 2 arguments instead of 4-5 args and because we can easily get the gridOptions and columnDefinitions from the grid object anyway.

For example, this PR has the following changes

Aurelia-Slickgrid.ts

// attach external sorting (backend) when available or default onSort (dataView)
if (gridOptions.enableSorting) {
-  (gridOptions.backendServiceApi || gridOptions.onBackendEventApi) ? this.sortService.attachBackendOnSort(grid, gridOptions) : this.sortService.attachLocalOnSort(grid, gridOptions, this.dataview, this.columnDefinitions);
+ (gridOptions.backendServiceApi || gridOptions.onBackendEventApi) ? this.sortService.attachBackendOnSort(grid, dataView) : this.sortService.attachLocalOnSort(grid, dataView);
}

Then in the SortService, it now changes to this

SortService.ts

-  attachLocalOnSort(grid: any, gridOptions: GridOption, dataView: any, columnDefinitions: Column[]) {
+  attachLocalOnSort(grid: any, dataView: any) {
+    this._isBackendGrid = false;
     this._grid = grid;
-    this._gridOptions = gridOptions;
+    this._dataView = dataView;
+    let columnDefinitions: Column[] = [];
+
+    if (grid) {
+      this._gridOptions = grid.getOptions();
+      columnDefinitions = grid.getColumns();
+    }

I think it worth to know about and I will merge this PR on Wednesday evening when I'm preparing the release. This should help in simplifying, though I'm not sure if it helps in any kind for the 2 grids in 1 page issue.

[jmzagorski]

that makes sense and might make it easier to refactor when reviewing the possibility of multiple grids. Thanks for the update