Jira: Add ability to add icons to issue remote links

[grahamalama]

Adds two parameters to Jira.create_or_update_issue_remote_links to support adding icons to remote links:

    "object": {                                            
        "url":"example.com/support?id=1",     
        "title":"TSTSUP-111",                                 
        "icon": {                                         
            "url16x16":"https://example.com/favicon.png",    
            "title":"Support Ticket"   
        },

see descriptions of these fields here.

[gonchik]

@grahamalama Thank you! :)