Distinguish legacy file actions from regular file actions

Legacy file actions are registered by legacy apps through
window.FileActions.register(). These actions can only be used by the
main file list ("all files") because legacy apps can only deal with a
single list / container.

New file actions of compatible apps must be registered through
OCA.Files.fileActions. These will be used for other lists like the
sharing overview.

Fixed versions and sharing actions to use OCA.Files.fileActions, which
makes them available in the sharing overview list.
Mimetype for sharing overview