Convert all the secret/storage encryption APIs / wire format to
handle UUIDs in raw format instead of non-canonical printable
format. Guarentees data format correctness.

* docs/schemas/storageencryption.rng: Make UUID mandatory for a secret
  and validate fully
* docs/schemas/secret.rng: Fully validate UUID
* include/libvirt/libvirt.h, include/libvirt/libvirt.h.in, Add
  virSecretLookupByUUID and virSecretGetUUID. Make
  virSecretGetUUIDString follow normal API design pattern
* python/generator.py: Skip generation of virSecretGetUUID,
  virSecretGetUUIDString and virSecretLookupByUUID
* python/libvir.c, python/libvirt-python-api.xml: Manual impl
  of virSecretGetUUID,virSecretGetUUIDString and virSecretLookupByUUID
* qemud/remote.c: s/virSecretLookupByUUIDString/virSecretLookupByUUID/
  Fix get_nonnull_secret/make_nonnull_secret to use unsigned char
* qemud/remote_protocol.x: Fix remote_nonnull_secret to use a
  remote_uuid instead of remote_nonnull_string for UUID field.
  Rename REMOTE_PROC_SECRET_LOOKUP_BY_UUID_STRING to
  REMOTE_PROC_SECRET_LOOKUP_BY_UUID_STRING and make it take an
  remote_uuid  value
* qemud/remote_dispatch_args.h, qemud/remote_dispatch_prototypes.h,
  qemud/remote_dispatch_ret.h, qemud/remote_dispatch_table.h,
  qemud/remote_protocol.c, qemud/remote_protocol.h: Re-generate
* src/datatypes.h, src/datatypes.c: Store UUID in raw format instead
  of printable. Change virGetSecret to use raw format UUID
* src/driver.h: Rename virDrvSecretLookupByUUIDString to
  virDrvSecretLookupByUUID and use raw format UUID
* src/libvirt.c: Add virSecretLookupByUUID and virSecretGetUUID
  and re-implement virSecretLookupByUUIDString and
  virSecretGetUUIDString in terms of those
* src/libvirt_public.syms: Add virSecretLookupByUUID and
  virSecretGetUUID
* src/remote_internal.c: Rename remoteSecretLookupByUUIDString
  to remoteSecretLookupByUUID. Fix typo in args for
  remoteSecretDefineXML impl. Use raw UUID format for
  get_nonnull_secret and make_nonnull_secret
* src/storage_encryption_conf.c, src/storage_encryption_conf.h:
  Storage UUID in raw format, and require it to be present in
  XML. Use UUID parser to validate.
* secret_conf.h, secret_conf.c: Generate a UUID if none is provided.
  Storage UUID in raw format.
* src/secret_driver.c: Adjust to deal with raw UUIDs. Save secrets
  in a filed with printable UUID, instead of base64 UUID.
* src/virsh.c: Adjust for changed public API contract of
  virSecretGetUUIDString.
* src/storage_Backend.c: DOn't undefine secret we just generated
  upon successful volume creation. Fix to handle raw UUIDs. Generate
  a non-clashing UUID
* src/qemu_driver.c: Change to use lookupByUUID instead of
  lookupByUUIDString

Sample session:

>>> import libvirt
>>> c = libvirt.open('qemu:///session')

>>> c.listSecrets()
['12247729-47d2-a783-88ce-b329d4781cd3', 'reee', 'abc']

>>> s = c.secretDefineXML("<secret ephemeral='no' private='no'>\n<description>Something for use</description>\n<volume>/foo/bar</volume>\n</secret>\n")

>>> s.UUIDString()
'340c2dfb-811b-eda8-da9e-25ccd7bfd650'

>>> s.XMLDesc()
"<secret ephemeral='no' private='no'>\n  <uuid>340c2dfb-811b-eda8-da9e-25ccd7bfd650</uuid>\n  <description>Something for use</description>\n  <volume>/foo/bar</volume>\n</secret>\n"

>>> s.setValue('abc\0xx\xffx')
0

>>> s.value()
'abc\x00xx\xffx'

>>> s.undefine()
0

* python/generator.py: Add rules for virSecret APIs
* python/libvir.c, python/libvirt-python-api.xml: Manual impl of
  virSecretSetValue, virSecretGetValue$ and virConnectListSecrets APIs
* python/libvirt_wrap.h, python/types.c: Wrapper for virSecret objects
* docs/libvirt-api.xml, docs/libvirt-refs.xml,
  docs/html/libvirt-virterror.html, docs/html/libvirt-libvirt.html,
  docs/devhelp/libvirt-virterror.html, docs/devhelp/libvirt-libvirt.html:
  Re-generate with 'make api'

  cleanups by Cole Robinson
Daniel

  Apply patch from Cole Robinson fixing UUIDString for python
Daniel

Saori FUKUTA).

  add a python binding for virNodeGetCellsFreeMemory
Daniel