#52. Discovered this bug.
#48. #50. Simplified drupalgap_goto() by adding drupalgap_goto_prepare_path(), drupalgap_page_in_dom() and drupalgap_goto_generate_page_and_go() functions. Added an optional options JSON object argument to drupalgap_goto(), setup default for form_submission. Adjusted drupalgap_goto to not remove the page from the dom if a form submission is happening. Adjusted drupalgap_entity_form_submit() to tell drupalgap_goto about the form submission.