Generate a .xe shell script which can upload to a xapi host/ XenServer

The script needs:
* the xe binary
* the xe-unikernel-upload binary
* a $HOME/.xe config file

Signed-off-by: David Scott <dave.scott@citrix.com>
chmod name.xe to 0o755

Signed-off-by: David Scott <dave.scott@citrix.com>
Bug fixes in generated .xe shell script

Signed-off-by: David Scott <dave.scott@citrix.com>
xe: make script more robust

  - add 'set -e' to stop on error
  - print the VDI, VM uuid (since the names aren't guaranteed to be unique)

Signed-off-by: David Scott <dave.scott@citrix.com>
xe: store the VIF uuid in a $VAR

  - avoids unnecessarily writing the bare UUID to the console
  - restores symmetry with VBD handling

Signed-off-by: David Scott <dave.scott@citrix.com>
Merge pull request #285 from djs55/xe

Generate a name.xe shell script to upload unikernel to a host running xapi (eg XenServer)