Feature: Bug tracker integration (right click on #Bug 1234 has option to open browser)

[adamk]

Adam K's old CVS Monitor tool provides a reference implementation of linking to arbitrary bug tracking systems by names or numbers.

For example, #RT 12345 gets linked to ​http://tracker/id=%s and so on.

Implement something similar for Padre, so that if you right click in a comment or pod (or perhaps just anywhere) and that click falls at a position that is part of a string that looks like a tracker link, provide a right-click menu option to open an external browser to the bug in question.

Provide a hash of tracker URLs in the project padre.yml file, since big projects will likely be the most common user.