fix refereeing reminders not being sent

fix appraisals count not showing
hide appraisal qualification count
prefer accepting offers of least overloaded fellow
skip deprecated test

fixes #26

fixes #340

test conditional assignment offer factories

fixes #339

fixes #337

fixes #338

complements #336

fixes #336

add assignment deadline extension button for edadmin/authors

fixes #335

fix crash on profile merge

add view permission checks for data export