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?

return both, count and result if the operation succeeded or failed. Maybe in some cases it is useful to know how much bytes where copied

using the number of writen bytes as indicator if streamCopy() was successfully. Instead check if fwrite returns the number of bytes or false

strrpos fails in cases the file in the path has no dot but the parent folder

Filesystem: use the updated Mount::findById in getPath to ensure we get the correct path if the storage is also mounted outside the view