Change the default layout to Equal

Problem/Motivation

I selected a 3 column grid. If you don't configure anything on the Choose your layout screen, and you save, you get three columns with no classes, and to the editor, they are full width. It appears broken.

This is because Advanced is the first choice, and I believe with that, you have to click the advanced button and add your own custom classes.

Steps to reproduce

1. Click the button in CKEditor to open the BS Grid dialog.
2. Select "Column 3" and click the Next button
3. On the Choose a layout screen click Save
4. Verify you do not get 3 columns side by side, but they are stacked instead. If you look at the source, you will see that they have no classes.

Proposed resolution

I propose that the default be changed from Advanced to Equal. That will provide the editor with the expectations of the first screen, and allow for further customization with the other options, then the advanced option at the end.

Steps to validate

1. Apply the patch, or checkout this MR
2. Click the button in CKEditor to open the BS Grid dialog.
3. Select "Column 3" and click the Next button
4. On the Choose a layout screen click Save
5. Verify the 3 columns are side by side
6. Repeat the process, this time expanding a width to verify Equal is selected
7. Repeat the process and try other settings and advanced to verify the rest of the existing functionality still works.