amara dev update 2014-05-17

Changes deployed to amara.org 2014-05-17

#1454 add_amara_description_credit_to_youtube called too often
#1477 Add filters to bulk approvals page
#1416 Add guard against task backlogs
#1019 Improve line-break support for TXT format
#1494 switch youtube sync from srt to sbv to avoid HTML tags display on youtube.