Address issue 486 - silent failure of unrecognized URI's added

in content/zotero/xpcom/attachments.js
- if the URI entered is unrecognized, added a user prompt allowing for editing and resubmission of the URI
- expanded the regular expression matching criteria to include URIs that start with 'www' and added a function to add 'http://' to the URI

in locale/en-US/zotero/zotero.properties
- added a string for the above prompt in the event of an unrecognized URI
Fixed bug which added a bad url (in addition to a 'good' url) to an attachment if they corrected the url in the prompt

Accomplished this by adding 2 'else if" statements to the match if statement.
cleared out unnecessary lines