Fix whitespace
Remove support for Gstreamer 1.0
Using GstFileMemAllocator to allocate memory for slots

The work on GstFileMemAllocator that uses mmap() to extend physical memory
available is available here:
https://github.com/kkonopko/gstreamer/tree/filemem-allocator
Fixed issue with buffer references

The ringbuffer holds a list of buffers used as memory containers (slots).
When a buffer is sent dowstream, it's actually supposed to be consumed and
disposed. To avoid that and reuse buffers need to copy them before sending
them downstream. The copy is a "shallow" copy though so the actual memory
is shared.
Minor patch for the dump_cache_state()

The state string LUT should have items reordered.
Removed all recording related code

Removing should be decoupled anyway and handled by a separate element.
Having this feature in the timeshifter itself only complicates it.

Now we are in a better position to test and improve it.

Other:
- fixed a regression: buffer metadata was not added so when buffer was
  consumed, the slot did not change its state from POP to RECYCLE (this is
  handled in metadata "dectructor": gst_slot_meta_free()

- returning gboolean from gst_shifter_cache_push as we need to indicate
  overrun situation

- renamed/removed any "recording" related entities to "temp" related to
  avoid confusion (recording is not intended to be an integral part of the
  timeshifter)
Fixed a regression: slots not recycled

Buffer metadata was not added so when a buffer was consumed, the slot did
not change its state from POP to RECYCLE (this is handled in metadata
"dectructor": gst_slot_meta_free())