[vsphere post processor] Make ResourcePool optional. Upload the template to an specific host

Local shell provisioner

provisioner/shell: retry file delete [GH-2286]

resume download after fail

/cc @cbednarski

builder/amazon-ebs: Clean up orphan volumes

/cc @pearkes - This fixes that crash

Fixes #1783

/cc @cbednarski - I try to do this after every PR just so I don't
forget, not a bad practice to get into. This is perhaps arguably an
"improvement" but I think due to the magnitude of code change I think
its worth it in the features sectin. :)

provisioner/puppet-server: Add ignore exit codes option

provisioner/shell: randomize default script name

post-processor/vagrant-cloud: retry uploads [GH-2167]

Added new compress post-processor from Vasiliy Tolstov