Support multiple environments

[olemp]

Support multiple environments.

An environment consists of:

• a mongodb connection string
• mongodb database name

[damsleth]

suggest taking a leaf out of the Heroku CLI book.

e.g
did tenant add - add tenant, with a backend structure like this (or similar)

tenants:
[{
  name : "puzzlepart",
  dbname : "main",
  connectionstring :"mongodb://......"
},
{
  name : "damsleth",
  dbname : "ddid",
  connectionstring :"mongodb://......"
},
]

did tenant list lists tenants
did tenant remove [name] removes tenant by name

And then for usage, when you run e.g. did import csv you get asked which tenant you want to use.
Could also save "selected tenant", so when you're running did import csv there's a message
current tenant is Puzzlepart before continuing