error_handler renamed to input_error_handler
Added static instance() method to default_basic_input_error_handler
Changed null_json_input_handler to empty_json_input_handler
const basic_parsing_context<Char>& becomes basic_parsing_context<Char> in input and input error handlers
Moved minimum_structure_capacity_ variable from basic_json_reader to basic_parsing_context
Dev of json_reader