Multi-Column Validation Number of Columns

[velkymx]

When setting up a multi-column layout, make sure that they columns always add up to 12. If they don't then a warning should be show. In addition, negative column number should not be allowed.

Steps to Reproduce:

1. go to a screen with a multicolumn
2. Set it to use 12 columns
3. Create a new entry on the JSON with a negative number
4. Add a column with the same value but positive using the GUI

Current Behavior:
The negative value subtracts from the total (6+6= 12, 12-6=6) allowing the user to input more columns

Expected Behavior:
User should not be able to use a negative row number on the JSON.

[el-nuru]

Working correctly on the screen builder project