Revise Contributing document
trashbin -> deleted files
minor cleanup for exception handling
use executeAudited in files cache
remove additional array wrapping
TL;DR and remove link from "Report issue here"
fix another double wrapped array
PDOException has no previous(), oh the consistency ...
Fix typo
Merge pull request #3586 from owncloud/contributing

Revise Contributing document
Merge pull request #3686 from owncloud/minor_exception_cleanup

minor cleanup for exception handling
Merge pull request #3690 from owncloud/use_execute_audited_in_filecache

use executeAudited in files cache
Merge branch 'master' into fixes_for_3641_3620