Allow opening the repl without opening the DB

[NullSoldier]

Summary

You can now use --no-db to not load the databases. This gives you access to the SDK without needing to load the data directory.

Testing Plan

Documentation

Does this change require any updates to the Iron Fish Docs (ex. the RPC API
Reference)? If yes, link a
related documentation pull request for the website.

[ ] Yes

Breaking Change

Is this a breaking change? If yes, add notes below on why this is breaking and
what additional work is required, if any.

[ ] Yes

[hughy]

I like the idea of this! Should we update the text that's logged on start if the db isn't open? Most (all?) of the examples won't work without a database

[NullSoldier]

I think it's fine, because those examples are still valid.

1. The examples show me how to do things
2. Only advanced user will use --no-opendb
3. They'll know to call node.open() if they want to use the DB
4. They'll get an nice error saying the DB is not open