Interactive config generator

[droserasprout]

dipdup new command currently can render one of templates with minor variations. Let's call it "from template" mode. We also need an "interactive mode". Start from empty config, then ask repetitive questions to construct config. Possible steps:

• Add contract -> Select kind -> Set address/hash -> Repeat?
• Add datasource -> Select kind -> Set URL/keys -> Repeat?
• Add index -> Select kind -> Select contracts/events ->Repeat?

When done, dump resulting YAML as a root config. There's a tricky thing in this task, compose-style env variables.