new folder structure for keys
all keys are now in files_encryption/key/path_to_file/filename/
share keys are named: user.shareKey
file key is named: fileKey
harmonize copyright notice
change private/public key names for consistency reasons
upgrade to new folder structure
delete old keys if file was moved to a different mount point
small fixes
Merge pull request #12382 from owncloud/enc_reorganize_folders2

[encryption] reorganize folder structure (second try to make Jenkins happy)