Entity import definition loses the static modifier when a field is added

If a entity (or any .java) is modified by Spring Roo and this file has an import static definition, the static modifier is lost when file is rewritten.

To test it:

1. create a new project using _clinic.roo: scrip
2. Edit Vet.java and add this import declaration:

   import static org.apache.commons.lang3.Validate.notBlank;
   

3. Use Roo field command to add a field to entity:

   field string --fieldName foo --class ~.domain.Vet
   

4. After Roo changes Vet.java, the previous import declaration will be this:

   import org.apache.commons.lang3.Validate.notBlank;