Add "Exclude enzymes found in the exclude region" feature

Add lable "Exclude" + combobox with two values: "region" and "enzymes found in the exclude region" to the "Search region" groupbox. Should be located approximatelly here:

Label + combobox should be enabled only when the "Exclude" checkbox is checked. The "region" value is a default one and corresponds to the current behavior.

if the "enzymes found in the region" is set, then you should:

1. Search for all enzymes in the "Exclude" region.
2. Search again in whole region, but without enzymes, which you found in the "Exclude" region on step 1.

If there are no sites were found on the step 2, text to log all these enzyme names.