better "drop database"

[eug3nix]

The current implementation of drop database functionality opens a new template-base tab and creates db backend.
This backend prevents database deletion.

[eug3nix]

I've added a workaround which allows dropping the database in most cases.
A proper solution would be:

1. Implement special "maintenance command" modal component which would be brought up for operation such as drop database.
2. Load SQL templates into this modal
3. Make it possible to execute such maintenance commands in context of another database to prevent creation of DB backend attached to the database we are working on