Cosmetic changes to the Filter Features page

[srp33]

Below is an example screenshot of this page.

I feel like the labels on this page should be simplified/adjusted. Please change the main label from "Filter Features" to "Select Variables" and remove the "Select Features" label. Please change the "Continue with these filters?" label to "Continue with these variables?"

While it is calculating the number of samples, the "Confirm" button is grayed out. Please also change the text on this button to "Calculating..." (and then change it to "Confirm" after the number of samples has been calculated successfully.