Merge pull request #533 from nabinhait/v4-hotfix

custom fields and report filters
hotfix: escape curly in boilerplate
fix --backup return code
email auth for exception mails
optimize mysqldump
Merge pull request #536 from pdvyas/hotfix

backup fixes
make celery emails config a dict
Merge pull request #537 from pdvyas/hotfix

make celery emails config a dict
Merged language patch with another patch global_defaults_to_system_settings