Joins to support queries

[drizk1]

• adds @create_view - db_table already supports using views
• adds drop_view
• adds support for joining a queried table with another queried table
• adds joining docs to outline using t() or @create_view for post wrangling joins
• bug fix to allow cross database/schema joins with duckdb
• corrects across name generation to be name_func to match TidierData, rather than func_name
  Breaking Change
• To enable post wrangling joins, all joins no longer accept bare table names. tables that exist on a db must be written as strings or symbols (ie "table.name" or :table)