Create separate user for GWM and give permissions for whoosh_index

This fixes #7 by creating a separate user account for GWM and setting apache to use that account when running GWM, and giving that user write permissions for whoosh_index. 
Do we want to default to using the apache user here? I can't remember if that's what we do in other places. It might make sense from a security point of view to default to making a gwm user instead.