(rasqal_cmdline_read_results): Added
Use rasqal_cmdline_read_results
Rename DEFAULT_RESULT_FORMAT_NAME_GRAPH to DEFAULT_RESULT_FORMAT_NAME
Add rasqal_cmdline_read_results
Only allow reading into query results of type bindings

(rasqal_query_results_formatter_read): Enforce that currently this
can ony read into bindings query results.
(rasqal_query_results_type_label): Added
Use rasqal_query_results_type_label() for better error messages
Use rasqal_query_results_type_label() for better error messages