Enhance pgimport/pgexport

Tasks:

• (pgimport) Fix --no-create-table so we don't need to pass =true
• (pgimport) Fix error when quotechar is detected as ' (the escape does not work)
• (pgexport) Be able to specify a query instead of table name, so we can export more complex data (this could be used to optimize rows query)
• (pgimport and pgexport) Be able to specify field names, like --fields
• (pgimport and pgexport) Be able to force the CSV dialect
• (pgimport and pgexport) Create docs
• (pgimport) If the table does not exist and we pass --no-create-table an error will not be raised. Decide if rows should raise an error and how PostgreSQL creates the table (field types)
• Update sequences (more info, possible solution)
• Check chunk size for some files (taking too long to detect dialect). Also, print "detecting CSV dialect" while it does not start)

Start by reviewing the pgimport and pgexport entry points and the remaining unchecked tasks in this issue, including the PostgreSQL sequence references. Break down the CSV dialect, field-name, table-creation, sequence, and chunk-size work separately; done means each selected behavior is implemented and verified for both commands where applicable.