[serverctl] rename remove_cube to drop_cube (closes #4545093)
For the sake of consistency, since commands are currently named:
- add_{cube,entity,attribute,relation}
- drop_{entity,attribute,relation}
- remove_cube
if repo.system_source.dbdriver == 'postgres':
sql('ALTER TABLE appears ADD COLUMN weight float')
sql('UPDATE appears SET weight=1.0 ')