[CHD-1419] Allow plugins to provide translation strings for Audit Log events

Well working on a plugin to add additional audit log events into my system I found myself running into a problem. It seems that when you display the field change_fields inside the audit log you run it though a simple translation system using the fields from the ticket database. This works well unless you are tiring to display information that does not have a field connected to a ticket like a comment or time tracking event or anything else a plug-in designer might think of using. Then that is where the fun begins. As it stands right now it tacks on a "t_" in front of the field then displays it. That "t_" make things really bad inside the display and really limits what a plug-in can do with the audit log. It would be really nice if the plugin could simple run the field un altered though the translation system as plug-in designers can add translatable strings in to the audit log making the audit log much more usable as being part of a tool kit. You ask how major of a change in the code do I need to do to get this added abilty. The answer is just 1 line of code.

Thanks
Robert.