on connection.delete() call, return the response
fixed typos in project.py file
add project.get_sli_manifest method that connect to API entry point to retrieve the SLI manifest for a given dataset
add a GetSLIManifestFailed exception
make the dataset call project.get_sli_manifest instead of creating its own manifest
remove now irrelevent parts of columns.py, that were useful to build the sli_manifest
change test_dataset to have  project tied to datasets
cleaned the maql generated by each different column
cleaned the MAQL generated by the whole dataset