Added the ability to support single selection in the selection plugin.

[fabanc]

The new code give the option to call the selection plugin so it supports either the selection of multiple rows, or one row at a time. The selection plugin expose three interfaces. One is for backward compatibility. They all share the same code base.

• RowSelection: same old interface for backward compatibility. Uses RowSelectionMultiple under the hood.
• RowSelectionSingle: new interface to support the selection of only one row at a time.
• RowSelectionMultiple: new interface to support the initial behaviour, i.e selection of multiple rows.

Automated test cases have been updated. A live demo is available here.

Load the plugin to support the selection of multiple rows:

			let multipleSelection = gridjs.plugins.selection.RowSelection;
			let grid = new gridjs.Grid({
				columns: [
					{
						id: 'select',
						name: 'Select',
						plugin: {
							component: multipleSelection 
						}
					 },
					 {
						id: 'a',
						name: 'Column A'
					 },
					 {
						id: 'b',
						name: 'Column B'
					 },
					 {
						id: 'c',
						name: 'Column C'
					 }
					],
				data: [
					[1, 2, 3],
					[4, 5, 6],
					[7, 8, 9],
					[10, 11, 12],
				],
				}).render(document.getElementById("mygrid"));

Load the plugin to support only the selection of one row at a time:

			let singleSelection = gridjs.plugins.selection.RowSelectionSingle;
			let grid = new gridjs.Grid({
				columns: [
					{
						id: 'select',
						name: 'Select',
						plugin: {
							component: singleSelection
						}
					 },
					 {
						id: 'a',
						name: 'Column A'
					 },
					 {
						id: 'b',
						name: 'Column B'
					 },
					 {
						id: 'c',
						name: 'Column C'
					 }
					],
				data: [
					[1, 2, 3],
					[4, 5, 6],
					[7, 8, 9],
					[10, 11, 12],
				],
				}).render(document.getElementById("mygrid"));