Allow unsetting multiple CMake variables

Desired behavior:

• Allow selecting multiple CMake cache variables
• Clicking the Unset button unsets all selected variables

With this approach I could search for CUDA_ then select all the variables and click unset. Right now I have to drop to a terminal in my build directory and do cmake -U 'CUDA_*' /path/to/build

Later on, maybe the Edit button could also work with multiple cache variables selected by popping up a batch edit window like is supported for editing multiple environment variables?