Add a FileInfo class which holds all info of a file and return that from getFileInfo, getDirectoryContent and search

Storage mount points are not deletable, so make sure that the unlink
operation and its hooks aren't run in such cases.

Note that some storages might recursively delete their contents when
calling unlink on their root. This fix prevents that as well.

Added argument to getFileInfo() to disable adding the size of
mountpoints to a directory's size.

Fixes #5924

Fixed permissions returned for mount points to not include update and
delete permissions.

Fixes #5291

otherwise the returned internalPath will not match followup calls to e.g. Cache::getID()

Conflicts:
	lib/private/vcategories.php

files: when filtering search results, ensure results are children of the fakeroot not just path starting the same

if a part file gets renamed to a real file, that this was the second step of a write operation, hence emit a write signal

on windows open resources will be locked while the stream is open.
closing the resource allows deletion below

rename isIgnoredFile to isPartialFile, remove check of blacklisted files in isPartialFile, correct usage of isPartialFile and isFileBlacklisted

revert changes to fbbc76f2 because master is very unstable right now

This is needed for WebDAV and FileSize
@samtuke and @schiesbn you guys know a better solution?