Scanner factory

[deadbits]

• Change scan status to use an Enum
• Scanners are initialized with keyword arguments, instead of the dictionary of kwargs they were previously passed
• Implement factory pattern to register and create scanner classes
• Add post_init hook for scanners to optionally use
• Decorator for registering scanners
  • requires_vectordb, requires_config, and requires_embedding can be specified for that scanner to receive additional options and classes it can use
• Remove some overly verbose log messages

Addresses #61 and #62