Questions can block tasks, to handle them automatically the driver can answers
them with the default answer. The auto_answer query parameter allows to enable
this automatic question handling.

* src/esx/README: add a detailed explanation for automatic question handling
* src/esx/esx_driver.c: add automatic question handling for all task related
  driver functions
* src/esx/esx_util.[ch]: add handling for the auto_answer query parameter
* src/esx/esx_vi.[ch], src/esx/esx_vi_methods.[ch], src/esx/esx_vi_types.[ch]:
  add new VI API methods and types and additional helper functions for
  automatic question handling

Replace free(virBufferContentAndReset()) with virBufferFreeAndReset().
Update documentation and replace all remaining calls to free() with
calls to VIR_FREE(). Also add missing calls to virBufferFreeAndReset()
and virReportOOMError() in OOM error cases.

A given domain XML gets converted to a VMX config, uploaded to the host
and registered as new virtual machine.

* src/esx/esx_driver.c: refactor datastore related path parsing into
  esxUtil_ParseDatastoreRelatedPath()
* src/esx/esx_util.[ch]: add esxUtil_ParseDatastoreRelatedPath()
* src/esx/esx_vi.[ch]: add esxVI_Context_UploadFile(), add datastores to
  the traversal in esxVI_BuildFullTraversalSpecList(), add
  esxVI_LookupDatastoreByName()
* src/esx/esx_vi_methods.[ch]: add esxVI_RegisterVM_Task()
* src/esx/esx_vi_types.c: make some error message more verbose
* src/esx/esx_vmx.[ch]: add esxVMX_AbsolutePathToDatastoreRelatedPath()
  to convert a path into a datastore related path, add esxVMX_ParseFileName()
  to convert from VMX path format to domain XML path format, extend the other
  parsing function to be datastore aware, add esxVMX_FormatFileName() to
  convert from domain XML path format to VMX path format, fix VMX ethernet
  entry formating
* tests/esxutilstest.c: add test for esxUtil_ParseDatastoreRelatedPath()
* tests/vmx2xmldata/*: update domain XML files to use datastore related paths
* tests/xml2vmxdata/*: update domain XML files to use datastore related paths,
  update VMX files to use absolute paths

Add esxVI_Occurence enum to describe expected occurence of items
* src/esx/esx_driver.c: update the use of esxVI_LookupVirtualMachineByUuid()
* src/esx/esx_vi.c: add an esxVI_Occurence parameter to
  esxVI_LookupVirtualMachineByUuid() and take care if esxVI_FindByUuid()
  can't find anything for a given uuid
* src/esx/esx_vi.h: add esxVI_Occurence enum
* src/esx/esx_vi_methods.c: expect null or more items to be returned
  from esxVI_FindByUuid()

* src/esx/esx_driver.c: add esxDomainUndefine() based on
  esxVI_UnregisterVM()
* src/esx/esx_vi_methods.[ch]: add esxVI_UnregisterVM()

* src/esx/esx_vi.[ch]: convert esxVI_RemoteRequest_Execute() to a
  simpler esxVI_Context_Execute() version, remove esxVI_RemoteRequest
  and convert esxVI_RemoteResponse to esxVI_Response
* src/esx/esx_vi_methods.c: update and simplify callers to use
  esxVI_Context_Execute() instead of esxVI_RemoteRequest_Execute()

* src/esx/esx_vi.[ch]: use virXPathNode*() in
  esxVI_RemoteRequest_Execute() and remove
  esxVI_RemoteResponse_DeserializeXPathObject*()
* src/esx/esx_vi_methods.c: update callers to use the new syntax of
  esxVI_RemoteRequest_Execute()

* src/esx/esx_*.[ch]: the driver, uses a remote minimal SOAP client
  to talk to the VI services on ESX nodes.
* configure.in include/libvirt/virterror.h src/Makefile.am src/driver.h
  src/libvirt.c src/virterror.c: glue in the new driver