in zotero/xpcom/attachments.js
  - created function cleanAttachmentURI
  - used same regex expressions from previous commit. Will address the matching code in subsequent commit

in zotero/zoteroPane.js
  - removed uri cleaning code (as it was transplanted to attachments.js
  - altered the prompt code to a 'while' statement so that continued submission of unrecognized uris prompts for a correction
  - added .trim() to submission statements to ensure entries contiaining only whitespace characters return false