Add option to exclude relationships

[DavidBoone]

Next to the current tables and columns exclude lists, adds support for relationships allowing relationships to be ignored by name in the same way.

Sorry, rushing this PR, but this has been very useful to me, so wanted to share before I forget :)

[pwelter34]

Looks great. Do you have a quick example of what you'd put in the yaml to skip a relationship?

[DavidBoone]

Looks great. Do you have a quick example of what you'd put in the yaml to skip a relationship?

Sure, here's a couple examples:

1. fully named relationship
2. just the relationship name (hope no other table happens to have a constraint of the same name!)
3. all relationships for the reseller table
4. all relationships in the reporting schema

database:
  provider: 'PostgreSQL'
  exclude:
    relationships:
      - public\.order\.order_reseller_id_fkey
      - order_reseller_id_fkey
      - public\.reseller\.
      - ^reporting\.