CCA wizard: do not display string columns at column selection step

[wlhunt]

String data is never processed by CCA, so don't wasted the space to display columns of string data that's present.

The parsing should detect that string columns are present, and the wizard should alert or inform the user that string data was discovered and is not valid for CCA and therefore not displayed in the CCA model creation process.

[wlhunt]

[wlhunt]

Above image example demonstrates grayed-out wizard info to be removed.

[wlhunt]

Initial suggested user alert:

Attention:
Slycat has detected non-numeric data columns in the given data table. The CCA calculation is only valid for numeric data so the non-numeric columns are not displayed.