Remove generator config and use generator db data

[shuse2]

Description

Using the new endpoints and commands, generator config is no longer required.

• Remove generator config from application config
• Remove generator config from ABI and related schema and handlers
• Update generator to use waitThreshold = blockTime / 5
• Update generator loadGenerators to load from DB, and set the private keys to keypairs in generator property if the keys are not encrypted

Acceptance Criteria

• Update all unit tests
• Check with DPoS examples if block generation works