BISERVER-11142 - Staging table not getting deleted when a datasource created using CSV File of Data Source Wizard is deleted

What was done:
1) fixed code for deserializing model
2) fixed method for deleting CSVs
3) adde call to te method deleting CSVs
Merge pull request #411 from kolinus/BISERVER-11142

BISERVER-11142 - Staging table not getting deleted when a datasource cre...