Implement auto inflation/deflation in the storage daemon.

This code implements automatic deflation (compression)
of data read or written to a device and automatic inflation
(uncompression) of data written or read from a device.

This allows you to do the following:

- Compress data on the FD send it to SD and write it to the device uncompressed.
- Send data uncompressed from the FD to the SD and write it to the device compressed.
- Read compressed data from a device and send it as uncompressed data to the FD.
- Read uncompressed data from a device and send it as compressed data to the FD.

This is implemented as a SD plugin.

Fixes #187: Implement auto inflation/deflation in storage daemon.
Switch to new version number.
Retry autochanger query for slots

In essence this is a bug in the firmware but it seems there are quite
some libraries which seem to be affected. We now retry the query one
more time when we get a zero slots returned.

Fixes #174: "status slots" says "0 slots" the first time after tapes
            were removed. Rerunning "status slots" then is correct.
Fix crash when an unsupported cipher is configured.