Add wrapper for NFD encoding workaround

Update imagePath to prefer theme, then app, then core images

imagePath updated so that image searches follow this priority:

1) /themes/$theme/apps/$app/img
2) /themes/$theme/$app/img
3) /themes/$theme/core/img
4) $appPath/img
5) /$app/img
6) /core/img

For each folder:
- if the specified file exists, use it.
- otherwise, if $basename.svg does NOT exist, try $basename.png
(This might better be "if filename was an svg, try the png"...)

Tests outside of tests/lib/ to PSR-4

Move federation app to PSR-4

flat federated re-share

Free up folder content from memory before recursing in the file scanner

Comments API is missing hook/event to allow other apps to register valid entities

Autoloader fix

Lock jobs while executing them, to allow multiple executors to run in…

Add interface methods for permission check for system tags

in case of federated re-shares the owner can be a remote user.
Therefore we can't always use to owner to access the local file

correctly accross share owner and share initiator