In FileBackend:

In FileBackend:
* Use 'b' param in some fopen() calls as needed for Windows and newline handling.
* Removed some useless padding code in FileBackend::getContainerShard(). Initialized $m to make IDE happy.
* Updated some code comments.
In SwiftFileBackend:
* Manually set the ETag when using php-cloudfiles for creating files to avoid https://github.com/rackspace/php-cloudfiles/issues/59.
* Manually set the content type based on how StreamFile::getType(). This makes it safe to read files directly out of the proxy to end-users. The streamFile() backend functions already uses a similar content-type check.