added unit tests for mailer
added lang files validition test
* fixed a variable name error in Setting * setting values to_s
removed broken route for sorting links
issue list: added 'Priority' column, removed 'Created on' column
post method verification for trackers/move
added the ability to set the sort order for trackers
added the ability to set the sort order for roles
removed png transparency (not supported in ie)
custom fields list screen split in 3 tabs (one for each kind of custom fields)
