clone_template has sane defaults for all providers

This is for smoke-testing templates on every provider, so making clone_template
as provider-agnostic as possible was needed.

Additional resulting changes:
- EC2 mgmt backend is able to deal with image names as well as AMIs, much as it does
  with instance names and IDs
- destroy_vm seemed generally useful, so it lives in utils.providers now
- minor cfme_data template changes, reflected in private yamls
Added pxe fields for Vsphere
Merge pull request #1069 from psav/fix_pxe_prov

Added pxe fields for Vsphere
Don't let exception bubble up from Pretty (even if obj's getattr is
broken)

Also fix wrong pretty_attr name
Merge branch 'master' of github.com:RedHatQE/cfme_tests
Added workaround for bug to be removed GH1070
Merge pull request #1071 from psav/fix_pxe_workaround

Added workaround for bug to be removed GH1070
Merge pull request #1053 from seandst/smoketester

clone_template has sane defaults for all providers