reenabled ghost tables

there are some things to review:
- how the ghost tables task is launched
- will it work with multiuser
- the user specs where not working
fixed search_for_cartodbfied_tables when the user has no tables
fixed, really
fixed get_cartodbfied_tables when there is not tables in user metadata database
fixed ruby lovely thing
fixed wrong condition
fixed spec
fixed specs
fixed specs
fixed when job is null
fixed resque checks
don't launch a migration when a table is registered
do ghost tables checks when the database has no tables
rename the visualization when the table is renamed
fixed table checking
reenabled ghost tables

there are some things to review:
- how the ghost tables task is launched
- will it work with multiuser
- the user specs where not working
fixed search_for_cartodbfied_tables when the user has no tables
fixed, really
fixed get_cartodbfied_tables when there is not tables in user metadata database
fixed ruby lovely thing