improve backend handling of duplicate issues
move duplicate issues into left list instead of separate tab
make issue status choices dependant on available outgoing workflow steps, implementing #2381,
also deprecating freelancing as a non-functional project setting, renaming functionality to allow setting status independantly of workflow
untablify attached files and links, also js-popupify link delete dialog
misc (very) minor bugfixes
make issue header scrolling fixer even smoother
improve attached image display in issue view
Fix invalid email headers

Issue report in http://issues.thebuggenie.com/thebuggenie/issues/2389
Merge pull request #281 from Oleh-Kravchenko/master

Fix invalid email headers
Don't set login "error" message on login page, since we're already there
add text input custom filters to supported interactive filters
add some css animations to the issue view when collapsing / expanding
add b2db support for having "in" join "on" criteria
add support for more custom fields in interactive search
improve searching for affected releases
add root installation workarounds as commented out lines in index.php
make sure subclasses entities are correctly initialized when selected by id
properly implement milestone, team and user custom fields
add support for showing / hiding milestones on issues and planning / roadmap pages (fixes issue #2392)
fix user dashboard not showing correct issues for dashboard views