New Feature: Conditional Toggling of Setting Fields

Hi, 

This is my recent addition for OptionTree. This feature hides/shows a certain field based on a specified condition of other fields.

Conditions can be specified by specifying the conditions on the UI builder.

Conditions can be like this:

    field_name:is(value)
    field_name:isnot(value)

So a particular field will be checked against other fields.

For now, the only working field to check against are dropdowns and radio buttons. Checkbox doesn't work yet because it needs a different logic. Other fields seems too complex and/or weird to be checked against. Lets limit only on those three fields.

Please do the necessary adjustments and optimizations if you want to implement this.

Thanks!