mime-type

chris steipp requested that:

* mimeTypeAndExtensionMatch doesn't ensure mime = extension.
  mimeTypeAndExtensionMatch() should use MimeMagic::isMatchingExtension()

* It looks like this is only used for the xml metadata. If so, can you please
  document that in the code?

* Use MimeMagic for mimetype detection in /Php/File.php

also adjust lines > 100 characters and removed no longer needed /Php/FileException.php

Change-Id: I2a5125b2e48c3d9dbc1fe7e58819804bef011b77