Replaced the trac specific ticket link with a general link.

Bug description: when you use the pushmanager create bookmarklet on a review
boad CR, jira tickets are not parsed correctly. They are thought to be trac
tickets, and an incorrect trac link is generated in the PR comments.

Ref: (PUSHMGR-63) Pushmanager Create does not parse jira issues correctly
Removed redundant comment on config example.

Removed a unecessary line describing the ticket_tracker_url_format field from the
config example file.
Test added for the ticket tracker url.

The automatic test now checks also the ticket tracker url (just tests that
the javascript contains the word %TICKET%).
Merge pull request #105 from fede1024/pushmgr-63

Replaced the trac specific ticket link with a general link.