DB access permission for user

[PaulPoulain]

In Urungi, permissions are not linked to DB access.
We should be able to have the following use case :

• 1 urungi setup
• 2 data sources DS1 and DS2 (same DB schema)
• UserA can do things on DS1, UserB can do things on DS2, UserC can do things on DS1 and DS2
  It also means that a report or a dashboard can be used by several datasource. The dashboard dash1 is created by UserC, who says the dashboard can be run against DS1 or DS2. It probably requires new concepts !

1st draft:

• add "alias" field to a data source. and alias can be duplicated. When you create a dashboard or a report, you link it to a data source name (current behavior) or a datasource alias.
• when you run a dashboard or a report linked to an alias, if you have permission to access to more than one DB with this alias, ask "which DB do you want to query" before running.
• alternatively : let the user chose which alias-space he want to apply all the reports/dashboards he will run.