Table calls sortInternalRows with externalSorting=true

[dmartin-gh]

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[ ] feature request
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Current behavior

When externalSorting is enabled, the sortInternalRows() method is still called due to this commit: https://github.com/swimlane/ngx-datatable/commit/67a4e8aeaf6c03e7fa3bc6a6d0a34725ec1c6b0a This causes the rows to change their sort order in undesirable ways after they are passed to the datatable component. Single sorting seems to work fine, but when combined with [sortType]="'multi'" the sort order is incorrect.

I believe the additional call to sortInternalRows() added to the translateColumns() method should be changed to:

if (!this.externalSorting) {
    this.sortInternalRows();
}

Expected behavior

Multi sorting would work correctly with externalSorting=true and the grid would never attempt to sort the rows itself.

Reproduction of the problem

Turn on [externalSorting]="true" and [sortType]="'multi'" and see that the sortInternalRows() method is called.

Please tell us about your environment:

• Table version: 11.3.0

• Angular version: 5.2.4

• Browser: Chrome 67.0.3396.99

• Language: TypeScript 2.5.3